CVE-2026-115889

criticalpriority · track · 10EPSS 0.005 · 39 %ileexploit · PoCUS
grimoire priorityP1 · Urgent
Exploitable?
Public exploit
1 exploit · PoC
Likely / severe?
0.45% (39th) EPSS
CVSS 9.9 · critical
Is it mine?
3 products
Check your exposure
Who says so?
1 sources
osv

EPSS · scored 2026-10-28

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

9.9
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · security-advisories@github.comexploitability 3.1 · impact 6
v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · OSV
v3.19.4criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:Psecondary · CVSS-BT (t0sche)
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-197USCWE-197USCWE-843USCWE-843US
04

exploits (1)

Public proof-of-concept and weaponised exploit code.

05

affected products (3)

Products and version ranges known to be affected.

06

advisories (2)

Vendor and ecosystem advisories describing this.

  • GHSA-897f-g5gm-fmxmWasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation2026-10-23ghsa · osvUS

    ## Summary In Wasmtime prior to v43, the Cranelift compiler backend bit-packs its SSA value indices in a way that can result in silent overflow in release builds, and result in incorrect value references in the IR resulting in arbitrary miscompilation. A very large Wasm function body, or one that is specially crafted to use many SSA values, can use this to force type-confusion or other arbitrary side-effects and escape the sandbox. Cranelift was changed in Wasmtime v43 to use a full `u32` index, with checks if that limit is exceeded, and so is no longer susceptible to this bug. ## Impact A Wasmtime engine with default settings (using the Cranelift backend) on any architecture/platform could experience a sandbox escape from a specially-crafted Wasm module. ## Patches Wasmtime v36.0.19 has been released which fixes this issue.

  • RUSTSEC-2026-0380Bit-packing in Cranelift compiler causes silent overflow and miscompilation2026-10-19vendor · osvUS

    This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm For more information see the GitHub-hosted security advisory.

07

also known as (2)

Other names and identifiers for this entity.

08

sources

Which sources assert this record, and when.

osvNVDCVE.orgMITRE
published 2026-10-23modified 2026-10-26
09

references (7) nvd

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan