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...
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
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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
squirrel3Debian:13 |
before 3.1-8.2+deb13u1, plus listed versions 3.1-8.2 |
3.1-8.2+deb13u1 |
squirrelMageia:8 |
before 3.2-1.mga8 | 3.2-1.mga8 |
supertuxMageia:8 |
before 0.6.2-4.2.mga8 | 0.6.2-4.2.mga8 |
squirrel3Ubuntu:18.04:LTS |
All versions, plus listed versions 3.1-43.1-5 |
None known |
squirrel3Ubuntu:20.04:LTS |
All versions, plus listed versions 3.1-83.1-8build1 |
None known |
squirrel3Ubuntu:22.04:LTS |
All versions, plus listed versions 3.1-8build1 |
None known |
squirrel3Ubuntu:25.10 |
All versions, plus listed versions 3.1-8.2 |
None known |
squirrel3Ubuntu:26.10 |
All versions, plus listed versions 3.1-8.33.1-8.43.1-8.5 |
None known |
squirrel3Ubuntu:26.04:LTS |
All versions, plus listed versions 3.1-8.23.1-8.3 |
None known |
squirrelSUSE:Package Hub 15 SP4 |
before 3.0.7-bp154.3.3.1 | 3.0.7-bp154.3.3.1 |
squirrelopenSUSE:Leap 15.4 |
before 3.0.7-bp154.3.3.1 | 3.0.7-bp154.3.3.1 |
squirrelopenSUSE:Tumbleweed |
before 3.2-1.1 | 3.2-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE 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
github.com/albertodemichelis/squirrel/commit/23a0620658714b996d20da3d4dd1a0dcf9b0bd98
squirrel-lang.org
blog.sonarsource.com/squirrel-vm-sandbox-escape
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BV7SJJ44AGAX4ILIVPREIXPJ2GOG3FKV
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M3FQILX7UUEERSDPMZP3MKGTMY2E7ESU
sonarsource.com/blog/squirrel-vm-sandbox-escape
Show 13 moreShow less
nvd.nist.gov/vuln/detail/CVE-2021-41556
lists.fedoraproject.org/archives/list/[email protected]/message/BV7SJJ44AGAX4ILIVPREIXPJ2GOG3FKV
lists.fedoraproject.org/archives/list/[email protected]/message/M3FQILX7UUEERSDPMZP3MKGTMY2E7ESU
github.com/advisories/GHSA-cm28-mc8h-9h49
security-tracker.debian.org/tracker/CVE-2021-41556
advisories.mageia.org/MGASA-2023-0150.html
bugs.mageia.org/show_bug.cgi?id=30742
lists.fedoraproject.org/archives/list/[email protected]/thread/M3FQILX7UUEERSDPMZP3MKGTMY2E7ESU
lists.opensuse.org/archives/list/[email protected]/thread/5NX6SWKNR7LNUXJROLGLSVD3ZEB4LUQY
ubuntu.com/security/CVE-2021-41556
cve.org/CVERecord?id=CVE-2021-41556
bugzilla.suse.com/1201974
suse.com/security/cve/CVE-2021-41556