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Public proof of conceptFix available

CVE-2021-41556

A public proof of concept exists; no exploitation attested.

  • Published2022-07-28
  • WeaknessCWE-125

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that can lead to Code Execution. If a victim executes an attacker-controlled squirrel script, it is possible for the attacker to break out of the squirrel script sandbox even if all dangerous functionality such as File System functions has been disabled. An attacker might abuse this bug to target (for example) Cloud services that allow customization via SquirrelScripts, or distribute malware through video games that embed a Squirrel Engine.

Timeline

dates in UTC
  1. 2022-07-2821:15CVE publishedNVD

Versions per branch

NVD
Fedoraproject fedora
BranchAffectedFixed in
35.x= 35no fix published
36.x= 36no fix published
Squirrel-lang squirrel
BranchAffectedFixed in
2.2≤ 2.2.5no fix published
3.x≥ 3.0, ≤ 3.1no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • squirrelSUSE:Package Hub 15 SP4all versions · fixed in 3.0.7-bp154.3.3.1
  • squirrelopenSUSE:Tumbleweedall versions · fixed in 3.2-1.1
  • squirrelopenSUSE:Leap 15.4all versions · fixed in 3.0.7-bp154.3.3.1
  • squirrelMageia:8all versions · fixed in 3.2-1.mga8
  • squirrel3Ubuntu:26.10all versions · no fixed version listed
  • squirrel3Ubuntu:26.04:LTSall versions · no fixed version listed
  • squirrel3Ubuntu:25.10all versions · no fixed version listed
  • squirrel3Ubuntu:22.04:LTSall versions · no fixed version listed

4 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-41556 Red Hat Product Security

    squirrel: out-of-bounds read in core interpreter allows sandbox escape leads to code execution

Full record on NVD

Fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Published
2022-07-28
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-cm28-mc8h-9h49

Frequently asked questions

What is CVE-2021-41556?

sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that can lead to Code Execution. If a victim executes an attacker-controlled squirrel script, it is possible for the attacker to break out of the squirrel script sandbox even if all dangerous functionality such as File System functions has been disabled. An attacker might abuse this bug to target (for example) Cloud services that allow customization via SquirrelScripts, or distribute malware through video games that embed a Squirrel Engine.

Is CVE-2021-41556 actively exploited?

A proof-of-concept exploit exists for CVE-2021-41556, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2021-41556?

CVE-2021-41556 has a CVSS v3 base score of 10 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

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Sources for this record