Summary
Workarounds
There is no known workaround for this issue and affected hosts/embeddings are recommended to upgrade.
Impact
Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration.
Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories.
A write operation targets a memory location beyond the intended buffer boundary. Typical impact: memory corruption, crash, or arbitrary code execution.
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-2026-35195? CVE-2026-35195 is a medium-severity out-of-bounds write 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. A write operation targets a memory location beyond the intended buffer boundary.
- Which versions of wasmtime are affected by CVE-2026-35195? wasmtime (rust) versions < 24.0.7 is affected.
- Is there a fix for CVE-2026-35195? Yes. CVE-2026-35195 is fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1. Upgrade to this version or later.
- Is CVE-2026-35195 exploitable, and should I be worried? Whether CVE-2026-35195 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-2026-35195 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-2026-35195?
- 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