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Fencer Intel
critical 9.9

CVE-2026-115889 json

Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation

published 21d ago modified 14d ago also EUVD-2026-109186 , GHSA-897f-g5gm-fmxm , RUSTSEC-2026-0380

cvss
9.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 39%
public exploits
0
none known

Summary

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 sandbox on any architecture using the default Cranelift backend. This issue is fixed in versions 36.0.19 and 43.0.0.

Patch / fix

  • crates.io wasmtime 36.0.19, 43.0.0
  • bytecodealliance wasmtime 36.0.19, 43.0.0
  • rust-wasmtime Debian 14 36.0.20+dfsg-1

debian advisories DEBIAN-CVE-2026-115889

  • rust Azure Linux 3.0 1.75.0-31
  • rust Azure Linux 3.0 1.98.1-1

azure linux advisories AZL-111431AZL-111437

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-115889 updated cvss 8.8

wasmtime: Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation

  • Red Hat Connectivity Link 1 rhcl-1/wasm-shim-rhel9 Red Hat Enterprise Linux 10 tree-sitter
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 10 virt-firmware-rs
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
14d ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
GitHub 3.1 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
OSV 3.1 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
crates.io wasmtime
<36.0.19
>=37.0.0, <43.0.0
>=0.0.0-0, <36.0.19
36.0.19
43.0.0

Affected products

  • bytecodealliance wasmtime

Classification

Weakness
  • CWE-197 Numeric Truncation Error
  • CWE-843 Access of Resource Using Incompatible Type

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.