CVE-2026-34945: Wasmtime is a runtime for WebAssembly

Routine

MEDIUM 6.5UPGRADE

CVE-2026-34945 is a medium-severity flaw (CVSS 6.5) affecting wasmtime. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size instruction. This bug could lead to disclosing data on the host's stack to WebAssembly guests. The host's stack can possibly contain sensitive data related to other host-originating operations which is not intended

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 75%)
CISA exploited list	No
Weakness	CWE-681
Published	2026-04-09
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: bytecodealliance

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-09 19:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

bytecodealliance wasmtime UPGRADE

Affected: >= 25.0.0 and < 36.0.7 · >= 37.0.0 and < 42.0.2 · >= 43.0.0 and < 43.0.1

Fixed in: 36.0.7, 42.0.2, 43.0.1

Safe to downgrade to: a release before 25.0.0

1. Check installed version

apt-cache policy wasmtime || rpm -q wasmtime || wasmtime --version

2. UPGRADE to 36.0.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade wasmtime

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wasmtime

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 25.0.0 (Debian / Ubuntu)

apt-cache madison wasmtime sudo apt install wasmtime=<VERSION_BEFORE_25.0.0> sudo apt-mark hold wasmtime

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list wasmtime sudo dnf downgrade wasmtime-<VERSION_BEFORE_25.0.0> sudo dnf versionlock add wasmtime

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34945?

wasmtime: upgrade to 36.0.7, 42.0.2, 43.0.1. Exact commands for each OS are on this page.

Is CVE-2026-34945 being exploited?

CVE-2026-34945 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34945 affect?

CVE-2026-34945 affects wasmtime. Severity is medium (CVSS 6.5). Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size inst

How urgent is CVE-2026-34945?

Priority 29/100. No elevated risk signals yet.

Related CVEs

CVE-2026-34987 CRITICAL 9.9 UPGRADE Wasmtime is a runtime for WebAssembly
CVE-2026-34946 HIGH 7.5 UPGRADE Wasmtime is a runtime for WebAssembly
CVE-2026-35186 HIGH 7.5 UPGRADE Wasmtime is a runtime for WebAssembly
CVE-2026-34971 HIGH 7.8 UPGRADE Wasmtime is a runtime for WebAssembly
CVE-2026-34988 MEDIUM 6.3 UPGRADE Wasmtime is a runtime for WebAssembly

References

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