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CVE-2023-27477

16
FAUCET Score

CVE-2023-27477 is a code generation bug in Wasmtime's Cranelift backend, specifically affecting the WebAssembly i8x16.select instruction on x86_64 platforms. This flaw, an off-by-one error in mask calculation, leads to incorrect results when specific conditions are met, impacting bytecodealliance cranelift-codegen and wasmtime. With a CVSS score of 4.3 (MEDIUM), the vulnerability has a network attack vector and low attack complexity, requiring low privileges and no user interaction. Its potential impact is limited to low integrity, with no confidentiality or availability impact. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this CVE. Users are advised to upgrade to Wasmtime versions 6.0.1, 5.0.1, or 4.0.1, or disable the Wasm SIMD proposal as a workaround.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.84.0, < 0.91.1CPE matchmatch criteria
cpe:2.3:a:bytecodealliance:cranelift-codegen:*:*:*:*:*:rust:*:*
0.92.0CPE matchmatch criteria
cpe:2.3:a:bytecodealliance:cranelift-codegen:0.92.0:*:*:*:*:rust:*:*
0.93.0CPE matchmatch criteria
cpe:2.3:a:bytecodealliance:cranelift-codegen:0.93.0:*:*:*:*:rust:*:*
>= 0.37.0, < 4.0.1CPE matchmatch criteria
cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:*
5.0.0CPE matchmatch criteria
cpe:2.3:a:bytecodealliance:wasmtime:5.0.0:*:*:*:*:rust:*:*

CVSS Data

CVSS version used by this source: 3.1

3.1LOW

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
1.6
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.62%
Probability of exploitation in next 30 days
EPSS Percentile
46.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0062 is in the 56th percentile among its peer group of 21,957 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (10)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: cbl2 rust 1.68.2-2 on CBL Mariner 2.0Fixed in: 1.68.2-2
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 1.68.2-2
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 1.68.2-2
rustpatch availablevia ghsa
Product: cranelift-codegenFixed in: 0.91.1
rustpatch availablevia ghsa
Product: cranelift-codegenFixed in: 0.92.1
rustpatch availablevia ghsa
Product: cranelift-codegenFixed in: 0.93.1
rustpatch availablevia ghsa
Product: wasmtimeFixed in: 4.0.1
rustpatch availablevia ghsa
Product: wasmtimeFixed in: 5.0.1
rustpatch availablevia ghsa
Product: wasmtimeFixed in: 6.0.1

Vendor Advisories (3)

microsoft2023-May/CVE-2023-27477

CVE-2023-27477

May 9, 2023
microsoft2023-Mar/CVE-2023-27477Moderate

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.

Mar 14, 2023
rustGHSA-xm67-587q-r2vwlow

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

Mar 9, 2023

References

docs.rs / wasmtime/latest/wasmtime/struct.Config.html
Product
github.com / bytecodealliance/wasmtime/commit/5dc2bbccbb363e474d2c9a1b8e38a89a43bbd5d1
Patch
github.com / bytecodealliance/wasmtime/security/advisories/GHSA-xm67-587q-r2vw
MitigationPatchVendor Advisory
github.com / webassembly/simd
Not Applicable
groups.google.com / a/bytecodealliance.org/g/sec-announce/c/Mov-ItrNJsQ
Mailing ListRelease NotesVendor Advisory