CVE-2023-27477Network attack vector

Guest execution corruption via incorrect SIMD shuffle mask

Published Mar 8, 2023 · Updated Feb 25, 2025

Off-by-one error in Cranelift for Wasmtime allows attackers to alter guest execution via crafted WebAssembly on x86_64 hosts. Cranelift's x86_64 lowering of i8x16.select subtracts 15 rather than 16 from second-vector lane indices when both operands are identical, producing an incorrect pshufb mask. Exploitation requires SIMD-enabled execution and the affected shuffle pattern; the flaw does not escape the guest sandbox but can change arguments passed to imported host functions.

CVSS severity3.1
Low
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Off-by-one error in Cranelift for Wasmtime allows attackers to alter guest execution via crafted WebAssembly on x86_64 hosts. Cranelift's x86_64 lowering of i8x16.select subtracts 15 rather than 16 from second-vector lane indices when both operands are identical, producing an incorrect pshufb mask. Exploitation requires SIMD-enabled execution and the affected shuffle pattern; the flaw does not escape the guest sandbox but can change arguments passed to imported host functions.

The record

CVE
CVE-2023-27477
Published
Mar 8, 2023
Updated
Feb 25, 2025
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-193
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 8, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=cranelift-codegen: >= 0.88.0, < 0.91.1
  2. Affected versionversion=cranelift-codegen: >= 0.92.0, < 0.92.1
  3. Affected versionversion=cranelift-codegen: >= 0.93.0, < 0.93.1
  4. Affected versionversion=wasmtime: >= 0.37.0, < 4.0.1
  5. Affected versionversion=wasmtime: >= 5.0.0, < 5.0.1
  6. Affected versionversion=wasmtime: >= 6.0.0, < 6.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Bytecode Alliance · Wasmtimeversion=cranelift-codegen: >= 0.88.0, < 0.91.1; version=cranelift-codegen: >= 0.92.0, < 0.92.1; version=cranelift-codegen: >= 0.93.0, < 0.93.1; version=wasmtime: >= 0.37.0, < 4.0.1; version=wasmtime: >= 5.0.0, < 5.0.1; version=wasmtime: >= 6.0.0, < 6.0.1

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
3.1GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-193Off-by-one Error

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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