Summary
Workarounds
There is no workaround for this bug. Hosts are recommended to updated to a patched version of Wasmtime.
Impact
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.
CVE-2026-34942 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (24.0.7, 36.0.7, 42.0.2, 43.0.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Wasmtime 24.0.7, 36.0.7, 42.0.2, and 43.0.1 have been issued to fix this bug. Users are recommended to update to these patched versions of Wasmtime.
Frequently Asked Questions
- What is CVE-2026-34942? CVE-2026-34942 is a medium-severity security vulnerability in wasmtime (rust), affecting versions < 24.0.7. It is fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1.
- How severe is CVE-2026-34942? CVE-2026-34942 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of wasmtime are affected by CVE-2026-34942? wasmtime (rust) versions < 24.0.7 is affected.
- Is there a fix for CVE-2026-34942? Yes. CVE-2026-34942 is fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1. Upgrade to this version or later.
- Is CVE-2026-34942 exploitable, and should I be worried? Whether CVE-2026-34942 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-34942 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-34942?
- Upgrade
wasmtimeto 24.0.7 or later - Upgrade
wasmtimeto 36.0.7 or later - Upgrade
wasmtimeto 42.0.2 or later - Upgrade
wasmtimeto 43.0.1 or later
- Upgrade