CVE-2026-115889: Wasmtime is a runtime for WebAssembly

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CRITICAL 9.9

CVE-2026-115889 is a critical-severity flaw (CVSS 9.9) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Wasmtime is a runtime for WebAssembly. Prior to 36.0.19 and 43.0.0, the Cranelift compiler backend bit-packs SSA value indices in a way that can silently overflow in release builds when compiling a sufficiently large or specially crafted Wasm function with many SSA values. The overflow can make Cranelift reference incorrect IR values, causing arbitrary miscompilation, type confusion, and other attacker-controlled effects that may escape the Wasm

Why this priority

Critical severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	n/a
CISA exploited list	No
Weakness	CWE-197, CWE-843
Published	2026-10-23
Last modified	2026-10-23

Publisher (CNA): GitHub, Inc.

Timeline

2026-10-23 22:16 UTCPublished CVE record published
2026-10-23 22:16 UTCUpdated Record last modified

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Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

References

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