CVE-2026-35186: Wasmtime is a runtime for WebAssembly

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-35186 is a high-severity flaw (CVSS 7.5) 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 backend contains a bug where translating the table.grow operator causes the result to be incorrectly typed. For 32-bit tables this means that the result of the operator, internally in Winch, is tagged as a 64-bit value instead of a 32-bit value. This invalid internal representation of Winch's compiler state compounds into further iss

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 88%)
CISA exploited list	No
Weakness	CWE-789
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

Fixed in: 36.0.7, 42.0.2

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-2026-35186?

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

Is CVE-2026-35186 being exploited?

CVE-2026-35186 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-2026-35186 affect?

CVE-2026-35186 affects wasmtime. Severity is high (CVSS 7.5). 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 backend contains a bug where translating the table.grow operator causes the result to be incorrectly typed. For 32-bit tables

How urgent is CVE-2026-35186?

Priority 34/100. High severity; Remotely exploitable, no login, no user action

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-2026-34971 HIGH 7.8 UPGRADE Wasmtime is a runtime for WebAssembly
CVE-2026-34945 MEDIUM 6.5 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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