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CVE-2026-115889VulnerabilityPublished

Cranelift compiler causes silent overflow · Wasmtime: Bit-packing

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-115889· Critical 9.9

Not known to be exploited · CVSS 9.9 Critical : upgrade to 43.0.0 or 36.0.19 as a priority.

Data as of 29 Oct 2026, 10:37 UTC

CVSS 3.1 base score
9.9Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.19.9
EPSS
0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 43.0.0, 36.0.19
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 29 Oct 2026.

What to do

Upgrade wasmtime and bytecodealliance/wasmtime to 43.0.0 or 36.0.19.

Affected software

ProductAffectedFixed in
bytecodealliancewasmtimeAffected
  • >=37.0.0 <43.0.0
Fixed in
  • 43.0.0
bytecodealliancewasmtimeAffected
  • <36.0.19
Fixed in
  • 36.0.19
GitHubbytecodealliance/wasmtimepkg:github/bytecodealliance/wasmtimeOther threatsAffected
  • <36.0.19
  • >=37.0.0 <43.0.0
Fixed in
  • 36.0.19
  • 43.0.0

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

AI-suggested

No specific mitigation steps are detailed in the available data.

Description

A vulnerability in Wasmtime's Cranelift compiler causes silent overflow and miscompilation due to bit-packing issues. This flaw can lead to incorrect program behavior without explicit errors or warnings.

References

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