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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...

10.0 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

2.92%Up 1.4 points since Jul 29, 2022
90%50%10%1%

What each source reports

NVD Score used 10.0

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.

Record
CVE-2021-41556
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-125
Updated
2026-11-02
CVE List 10.0

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.

Record
CVE-2021-41556
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-125
Updated
2026-11-02
EUVDEUVD-2021-28574 10.0

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.

Record
EUVD-2021-28574
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-cm28-mc8h-9h49 10.0

sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the...

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.

Record
GHSA-cm28-mc8h-9h49
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-125
Updated
2026-11-02
OSV 10.0

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.

Record
CVE-2021-41556
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2021-41556 10.0

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.

Record
DEBIAN-CVE-2021-41556
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
Show 4 moreShow less
OSVUBUNTU-CVE-2021-41556 10.0

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.

Record
UBUNTU-CVE-2021-41556
CVSS 3.1
10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
OSVMGASA-2023-0150 No score

Updated squirrel/supertux packages fix security vulnerability

sqclass.cpp in Squirrel 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. (CVE-2021-41556)

supertux has been rebuilt as it uses a bundled copy of squirrel.

Record
MGASA-2023-0150
Updated
2026-11-02
OSVopenSUSE-SU-2023:0080-1 No score

Security update for squirrel

This update for squirrel fixes the following issues:

  • CVE-2021-41556: fix out-of-bounds read issue (boo#1201974)
Record
openSUSE-SU-2023:0080-1
Updated
2026-11-02
OSVopenSUSE-SU-2024:12611-1 No score

squirrel-3.2-1.1 on GA media

These are all security issues fixed in the squirrel-3.2-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:12611-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
squirrel3
Debian:13
before 3.1-8.2+deb13u1, plus listed versions
3.1-8.2
3.1-8.2+deb13u1
squirrel
Mageia:8
before 3.2-1.mga8
3.2-1.mga8
supertux
Mageia:8
before 0.6.2-4.2.mga8
0.6.2-4.2.mga8
squirrel3
Ubuntu:18.04:LTS
All versions, plus listed versions
3.1-43.1-5
None known
squirrel3
Ubuntu:20.04:LTS
All versions, plus listed versions
3.1-83.1-8build1
None known
squirrel3
Ubuntu:22.04:LTS
All versions, plus listed versions
3.1-8build1
None known
squirrel3
Ubuntu:25.10
All versions, plus listed versions
3.1-8.2
None known
squirrel3
Ubuntu:26.10
All versions, plus listed versions
3.1-8.33.1-8.43.1-8.5
None known
squirrel3
Ubuntu:26.04:LTS
All versions, plus listed versions
3.1-8.23.1-8.3
None known
squirrel
SUSE:Package Hub 15 SP4
before 3.0.7-bp154.3.3.1
3.0.7-bp154.3.3.1
squirrel
openSUSE:Leap 15.4
before 3.0.7-bp154.3.3.1
3.0.7-bp154.3.3.1
squirrel
openSUSE:Tumbleweed
before 3.2-1.1
3.2-1.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-41556 is a critical vulnerability (CVSS 10.0) in Squirrel-lang Squirrel, published July 28, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.92%, the 87th percentile. Fixed in squirrel3 3.1-8.2+deb13u1.

References

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