CVE-2026-34942 (GCVE-0-2026-34942)

Vulnerability from cvelistv5 – Published: 2026-04-09 18:32 – Updated: 2026-04-09 19:36
VLAI
Title
Wasmtime panics when transcoding misaligned utf-16 strings
Summary
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Severity
5.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-09 19:35 UTC
CWE
  • CWE-129 - Improper Validation of Array Index
Assigner
References
Impacted products
Vendor Product Version
bytecodealliance wasmtime Affected: < 24.0.7
Affected: >= 25.0.0, < 36.0.7
Affected: >= 37.0.0, < 42.0.2
Affected: >= 43.0.0, < 44.0.1
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