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CVE-2026-24116VulnerabilityPublished

CVE-2026-24116: bytecodealliance wasmtime · Out-of-bounds Read

Affects bytecodealliance wasmtimeSource CVE Database V5

0

Not known to be exploited · CVSS 4.1 Medium : upgrade to 40.0.3 or 36.0.5 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score
4.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 40.0.3, 36.0.5
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Jan 2026

  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 2026-10-25.

What to do

Upgrade bytecodealliance wasmtime to 40.0.3 or 36.0.5.

Affected software

ProductAffectedFixed in
bytecodealliancewasmtimeAffected
  • >=29.0.0 <36.0.5
  • >=37.0.0 <40.0.3
  • =41.0.0
Fixed in
  • 40.0.3
  • 36.0.5
crates.iobytecodealliance/wasmtimepkg:cargo/bytecodealliance/wasmtimeOther threatsAffected
  • =41.0.0
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 prioritize upgrading Wasmtime to the fixed versions 36.0.5, 40.0.3, or 41.0.1 depending on their current major version. If immediate upgrading is not feasible, enabling signals-based traps in Wasmtime configuration can serve as an effective interim mitigation to catch out-of-bounds memory accesses and prevent crashes. Organizations must avoid disabling guard pages, as this weakens sandbox protections and may expose systems to further risks. It is advisable to audit all WebAssembly workloads running on Wasmtime to identify affected versions and assess exposure. Implementing runtime monitoring to detect segmentation faults or abnormal crashes related to Wasmtime can help in early detection of exploitation attempts or instability. Additionally, organizations should review their use of Cranelift and WebAssembly instruction sets to understand if f64.copysign is commonly used in their workloads, as this instruction triggers the vulnerability. Security teams should maintain awareness of updates from the Bytecode Alliance and subscribe to vulnerability advisories to promptly apply patches. Finally, integrating Wasmtime runtime updates into regular patch management and DevOps pipelines will reduce future exposure to similar vulnerabilities.

Description

Wasmtime is a runtime for WebAssembly. Starting in version 29.0.0 and prior to version 36.0.5, 40.0.3, and 41.0.1, on x86-64 platforms with AVX, Wasmtime's compilation of the `f64.copysign` WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages disabled it's possible for out-of-sandbox data to be loaded, but unless there is another bug in Cranelift this data is not visible to WebAssembly guests. Wasmtime 36.0.5, 40.0.3, and 41.0.1 have been released to fix this issue. Users are recommended to upgrade to the patched versions of Wasmtime. Other affected versions are not patched and users should updated to supported major version instead. This bug can be worked around by enabling signals-based-traps. While disabling guard pages can be a quick fix in some situations, it's not recommended to disabled guard pages as it is a key defense-in-depth measure of Wasmtime.

References

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