CVE-2025-66627: Wasmi is a WebAssembly interpreter focused on constrained and embedded systems

Routine

HIGH 8.4UPGRADE

CVE-2025-66627 is a high-severity flaw (CVSS 8.4) affecting wasmi. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Wasmi is a WebAssembly interpreter focused on constrained and embedded systems. In versions 0.41.0, 0.41.1, 0.42.0 through 0.47.1, 0.50.0 through 0.51.2 and 1.0.0, Wasmi's linear memory implementation leads to a Use After Free vulnerability, triggered by a WebAssembly module under certain memory growth conditions. This issue potentially leads to memory corruption, information disclosure, or code execution. This issue is fixed in versions 0.41.2,

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.4 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 96%)
CISA exploited list	No
Weakness	CWE-416
Published	2025-12-09
Last modified	2026-10-14

Publisher (CNA): GitHub, Inc. · Vendor: wasmi-labs

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-09 16:18 UTCPublished CVE record published
2026-10-14 21:10 UTCUpdated Record last modified

wasmi-labs wasmi UPGRADE

Affected: >= 0.41.0 and < 0.41.2 · >= 0.47.0 and < 0.47.1 · >= 0.51.0 and < 0.51.3 · 1.0.0

Fixed in: 0.41.2, 0.47.1, 0.51.3

Safe to downgrade to: a release before 0.41.0

1. Check installed version

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

2. UPGRADE to 0.41.2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wasmi

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 0.41.0 (Debian / Ubuntu)

apt-cache madison wasmi sudo apt install wasmi=<VERSION_BEFORE_0.41.0> sudo apt-mark hold wasmi

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

dnf --showduplicates list wasmi sudo dnf downgrade wasmi-<VERSION_BEFORE_0.41.0> sudo dnf versionlock add wasmi

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-2025-66627?

wasmi: upgrade to 0.41.2, 0.47.1, 0.51.3. Exact commands for each OS are on this page.

Is CVE-2025-66627 being exploited?

CVE-2025-66627 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-2025-66627 affect?

CVE-2025-66627 affects wasmi. Severity is high (CVSS 8.4). Wasmi is a WebAssembly interpreter focused on constrained and embedded systems. In versions 0.41.0, 0.41.1, 0.42.0 through 0.47.1, 0.50.0 through 0.51.2 and 1.0.0, Wasmi's linear memory implementation leads to a Use After Free vulnerability

How urgent is CVE-2025-66627?

Priority 30/100. High severity

Related CVEs

CVE-2024-28123 HIGH 7.3 UPGRADE Wasmi is an efficient and lightweight WebAssembly interpreter with a focus on constrained and embedded systems

References

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