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Fencer Vulns
critical 10.0

CVE-2021-41556 json

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 Exec…

published 2022-07-28 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-28574

cvss
10.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.9%
EPSS 2.9% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

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.

Patch / fix

  • squirrel3 Debian 13 3.1-8.2+deb13u1

debian advisories DEBIAN-CVE-2021-41556

  • squirrel openSUSE Tumbleweed 3.2-1.1
  • squirrel Package Hub 15 SP4, openSUSE Leap 15.4 3.0.7-bp154.3.3.1

opensuse advisories openSUSE-SU-2024:12611-1openSUSE-SU-2023:0080-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-41556 updated cvss 8.6

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

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
5 mo ago

Exploit prediction

2.92% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • sonarsource.com https://www.sonarsource.com/blog/squirrel-vm-sandbox-escape/ referenced PoC, tagged "exploit" by a source, unverified
  • blog.sonarsource.com https://blog.sonarsource.com/squirrel-vm-sandbox-escape/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CNA 3.1 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.