How severe is CVE-2026-34946?

No CVSS score has been assigned to CVE-2026-34946 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34946?

CVE-2026-34946 affects the following packages: wasmtime (crates.io), wasmtime (crates.io), wasmtime (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2026-34946?

Update wasmtime to 36.0.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34946 is resolved across your whole dependency graph.

How do I detect CVE-2026-34946 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-2026-34946 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-34946 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34946 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-2026-34946?

CVE-2026-34946 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th 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-2026-34946?

CVE-2026-34946 is classified as CWE-670 (CWE-670). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34946 published, and has it been updated?

CVE-2026-34946 was published on April 9, 2026 and was last updated on October 28, 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-2026-34946 — wasmtime

CVE-2026-34946 is a CWE-670 vulnerability in wasmtime. A fix is available for wasmtime — see the affected versions and patch details below.

Wasmtime's host panics when Winch compiler executes `table.fill`

Also known asGHSA-q49f-xg75-m9xwRUSTSEC-2026-0089

Published

Apr 9, 2026

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 6, 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-2026-34946.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

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

Real-World Exposure

3 pkgs affected

🦀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

Impact

Wasmtime's Winch compiler contains a vulnerability where the compilation of the table.fill instruction can result in a host panic. This means that a valid guest can be compiled with Winch, on any architecture, and cause the host to panic. This represents a denial-of-service vulnerability in Wasmtime due to guests being able to trigger a panic.

The specific issue is that a historical refactoring, #11254, changed how compiled code referenced tables within the table.* instructions. This refactoring forgot to update the Winch code paths associated as well, meaning that Winch was using the wrong indexing scheme. Due to the feature support of Winch the only problem that can result is tables being mixed up or nonexistent tables being used, meaning that the guest is limited to panicking the host (using a nonexistent table), or executing spec-incorrect behavior and modifying the wrong table.

Patches

Wasmtime 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

Users of Cranelift are not affected by this issue, but for users of Winch there is no workaround for this bug. Hosts are recommended to updated to a patched version of Wasmtime.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀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 · 3 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 36.0.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34946 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

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-2026-34946 (CC BY 4.0)

Frequently Asked Questions

### Impact Wasmtime's Winch compiler contains a vulnerability where the compilation of the `table.fill` instruction can result in a host panic. This means that a valid guest can be compiled with Winch, on any architecture, and cause the host to panic. This represents a denial-of-service vulnerability in Wasmtime due to guests being able to trigger a panic. The specific issue is that a historical refactoring, #11254, changed how compiled code referenced tables within the `table.*` instructions. This refactoring forgot to update the Winch code paths associated as well, meaning that Winch was u

O3 Security · Impact-Aware SCA

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