CVE-2026-54786: Wasmtime is a runtime for WebAssembly

Routine

MEDIUM 5.0UPGRADE

CVE-2026-54786 is a medium-severity flaw (CVSS 5.0) 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. All versions prior to 24.0.10; versions 25.0.0 through those before 36.0.11; versions 37.0.0 through those before 44.0.3; and versions 45.0.0 and 45.0.1 contain a native implementation of WASIp1 which suffers from a leak in the fd_renumber function where the file descriptor being renumbered to is not properly closed. Wasmtime's implementation erroneously only updated the table of descriptors for WASIp1 and

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.0 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-400, CWE-772
Published	2026-07-01
Last modified	2026-10-25

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

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-01 21:17 UTCPublished CVE record published
2026-10-25 16:10 UTCUpdated Record last modified

bytecodealliance wasmtime UPGRADE

Affected: < 24.0.10 · >= 25.0.0 and < 36.0.11 · >= 37.0.0 and < 44.0.3 · >= 45.0.0 and < 45.0.2

Fixed in: 24.0.10, 36.0.11, 44.0.3, 45.0.2

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 24.0.10 (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-2026-54786?

wasmtime: upgrade to 24.0.10, 36.0.11, 44.0.3, 45.0.2. Exact commands for each OS are on this page.

Is CVE-2026-54786 being exploited?

CVE-2026-54786 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-2026-54786 affect?

CVE-2026-54786 affects wasmtime. Severity is medium (CVSS 5.0). Wasmtime is a runtime for WebAssembly. All versions prior to 24.0.10; versions 25.0.0 through those before 36.0.11; versions 37.0.0 through those before 44.0.3; and versions 45.0.0 and 45.0.1 contain a native implementation of WASIp1 which

How urgent is CVE-2026-54786?

Priority 25/100. No elevated risk signals yet.

References

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