How severe is CVE-2026-34941?

No CVSS score has been assigned to CVE-2026-34941 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34941?

CVE-2026-34941 affects the following packages: wasmtime (crates.io), wasmtime (crates.io), wasmtime (crates.io), wasmtime (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2026-34941?

Update wasmtime to 24.0.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34941 is resolved across your whole dependency graph.

How do I detect CVE-2026-34941 in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34941 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2026-34941 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34941 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34941?

CVE-2026-34941 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 34th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34941?

CVE-2026-34941 is classified as Out-of-bounds Read (CWE-125). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34941 published, and has it been updated?

CVE-2026-34941 was published on April 9, 2026 and was last updated on October 31, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

Not in CISA KEV

CVE-2026-34941 — wasmtime

CVE-2026-34941 is a Out-of-bounds Read vulnerability in wasmtime. A fix is available for wasmtime — see the affected versions and patch details below.

Wasmtime has a Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding

Also known asGHSA-hx6p-xpx3-jvvvRUSTSEC-2026-0093

Published

Apr 9, 2026

Updated

Oct 31, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34941.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

4 pkgs affected

🦀wasmtime🦀wasmtime🦀wasmtime🦀wasmtime

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte length, which is twice the size of the code units.

This vulnerability can cause the host to read beyond the end of a WebAssembly's linear memory in an attempt to transcode nonexistent bytes. In Wasmtime's default configuration this will read unmapped memory on a guard page, terminating the process with a segfault. Wasmtime can be configured, however, without guard pages which would mean that host memory beyond the end of linear memory may be read and interpreted as UTF-16.

A host segfault is a denial-of-service vulnerability in Wasmtime, and possibly being able to read beyond the end of linear memory is additionally a vulnerability. Note that reading beyond the end of linear memory requires nonstandard configuration of Wasmtime, specifically with guard pages disabled.

Impact

This is an out-of-bounds memory access. Any user running untrusted wasm components that use cross-component string passing (with UTF-16 source and latin1+utf16 destination encodings) is affected.

With guard pages: Denial of service. The host process crashes with SIGBUS/SIGSEGV.
Without guard pages: Potential information disclosure. The guest can read host memory beyond its linear memory allocation.

Patches

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. Workarounds

There is no workaround for this bug. Hosts are recommended to updated to a patched version of Wasmtime.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`wasmtime`	all versions	24.0.7`cargo update -p wasmtime --precise 24.0.7`
🦀crates.io	`wasmtime`	≥ 25.0.0&&< 36.0.7	36.0.7`cargo update -p wasmtime --precise 36.0.7`
🦀crates.io	`wasmtime`	≥ 37.0.0&&< 42.0.2	42.0.2`cargo update -p wasmtime --precise 42.0.2`
🦀crates.io	`wasmtime`	≥ 43.0.0&&< 43.0.1	43.0.1`cargo update -p wasmtime --precise 43.0.1`

Affected Products

1 product · 4 configurations

Application

wasmtimebytecodealliance

≥ 43.0.0 && < 43.0.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update wasmtime to 24.0.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34941 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-34941 (CC BY 4.0)

Frequently Asked Questions

### Summary Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte length, which is twice the size of the code units. This vulnerability can cause the host to read beyond the end of a WebAssembly's linear memory in an attempt to transcode nonexistent bytes. In Wasmtime's default configuration this will read unmapped memory on a guard page, terminating the process

O3 Security · Impact-Aware SCA

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