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Description

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.

PUBLISHED Reserved 2026-03-31 | Published 2026-04-09 | Updated 2026-04-09 | Assigner GitHub_M




MEDIUM: 5.9CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

Problem types

CWE-129: Improper Validation of Array Index

Product status

< 24.0.7
affected

>= 25.0.0, < 36.0.7
affected

>= 37.0.0, < 42.0.2
affected

>= 43.0.0, < 44.0.1
affected

References

github.com/...smtime/security/advisories/GHSA-jxhv-7h78-9775

cve.org (CVE-2026-34942)

nvd.nist.gov (CVE-2026-34942)

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