GHSA-897f-g5gm-fmxm: wasmtime (CVE-2026-115889)

Bit-packing in Cranelift compiler causes silent overflow and miscompilation

CVSS 9.9 CriticalCriticalEPSS 0.0045 · 39th percentile

Critical, because:

CVSS score 9.9: 9.0 or more.

Published by the GitHub Advisory Database at 19 Oct 2026, 12:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

Package	Ecosystem	Affected	Fixed in
wasmtime	crates.io	>=0.0.0-0, <36.0.19 \|\| >=37.0.0, <43.0.0	36.0.19, 43.0.0

Identifiers

GHSA-897f-g5gm-fmxm · CVE-2026-115889 · RUSTSEC-2026-0380

Weakness (CWE)

CWE-197 · CWE-843

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Wasmtime versions before 36.0.19, and versions 37.0.0 up to 43.0.0, are affected by a bug in bit-packing within the Cranelift compiler that causes silent integer overflow and miscompilation. The source gives few details about how an attacker would trigger it or what they could achieve. Upgrade to Wasmtime 36.0.19 or 43.0.0 to fix the issue.

Written 3 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
9.9	Critical	3.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0045, the 39th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:24 UTC First seen by agentprime
31 Oct 2026, 14:24 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.