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VulnerabilityPublished

CVE-2025-66627: wasmi · Use After Free

Affects wasmiSource CVE Database V5

0

Not known to be exploited · CVSS 8.4 High · fixed in 0.41.2 : patch wasmi soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score
8.4High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.41.2
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Dec 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
crates.iowasmi-labs/wasmipkg:cargo/wasmi-labs/wasmiOther threatsAffected
  • =0.41.0
  • =0.41.1
  • >=0.42.0 <=0.47.1
  • >=0.50.0 <=0.51.2
  • =1.0.0
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately assess their use of wasmi and identify affected versions within their embedded or constrained systems. The primary mitigation is to upgrade to patched versions: 0.41.2, 0.47.1, 0.51.3, or 1.0.1. Where upgrading is not immediately feasible, organizations should implement strict limits on the maximum linear memory sizes allocated to WebAssembly modules to reduce the risk of triggering the vulnerability. Additionally, applying runtime memory protections and monitoring for anomalous WebAssembly module behavior can help detect exploitation attempts. Network segmentation and strict access controls around devices running wasmi can limit exposure. Organizations should also review supply chain dependencies to ensure no indirect exposure via third-party components. Finally, maintaining up-to-date threat intelligence and preparing incident response plans for potential exploitation scenarios will enhance resilience.

Description

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, 0.47.1, 0.51.3 and 1.0.1. To workaround this issue, consider limiting the maximum linear memory sizes where feasible.

References

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