CVE-2021-41556

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

2.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-09-22 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2022-07-28 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 04:08 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.9% in the next 30 days (EPSS).
• Severity: 10.0 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2022-07-28 21:15 UTC

Last modified

2026-06-17 04:08 UTC

Exploit probability

2.9% · EPSS, next 30 days

Weakness

CWE-125 · Out-of-bounds read

Record status

Modified

Affected

• squirrel-lang Squirrel ≤ 2.2.5
• squirrel-lang Squirrel ≤ 3.1
• Fedoraproject Fedora 35
• Fedoraproject Fedora 36

Attack profile CVSS 3.1 · 10.0

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-41556.md and follow it. Check whether this project is affected by CVE-2021-41556. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge