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Fencer Vulns
low 3.1

CVE-2023-27477 json

wasmtime vulnerable to miscompilation of `i8x16.select` with the same inputs on x86_64

published 2023-03-03 3 y ago modified 2026-10-12 27 d ago also GHSA-xm67-587q-r2vw , RUSTSEC-2023-0093 , EUVD-2023-1143

cvss
3.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's code generation backend, Cranelift, has a bug on x86_64 platforms for the WebAssembly `i8x16.select` instruction which will produce the wrong results when the same operand is provided to the instruction and some of the selected indices are greater than 16. There is an off-by-one error in the calculation of the mask to the `pshufb` instruction which causes incorrect results to be returned if lanes are selected from the second vector. This codegen bug has been fixed in Wasmtiem 6.0.1, 5.0.1, and 4.0.1. Users are recommended to upgrade to these updated versions. If upgrading is not an option for you at this time, you can avoid this miscompilation by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other platforms such as AArch64 and s390x are not affected.

Patch / fix

  • crates.io wasmtime 4.0.1, 5.0.1, 6.0.1
  • crates.io cranelift-codegen 0.91.1, 0.92.1, 0.93.1
  • bytecodealliance cranelift-codegen 0.91.1
  • bytecodealliance wasmtime 4.0.1
  • rust CBL-Mariner 2.0 1.68.2-2

azure linux advisories AZL-25857

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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
OSV 3.1 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
GitHub 3.1 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
crates.io wasmtime
>=1.0.0, <4.0.1
>=5.0.0, <5.0.1
>=6.0.0, <6.0.1
>=0.0.0-0, <4.0.1
4.0.1
5.0.1
6.0.1
crates.io cranelift-codegen
>=0.88.0, <0.91.1
>=0.92.0, <0.92.1
>=0.93.0, <0.93.1
0.91.1
0.92.1
0.93.1

Affected products

  • bytecodealliance wasmtime

Classification

Weakness

References

Sources

Fencer Vulns 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.