# CVE-2026-9541: Squirrel ReadObject heap buffer overflow in Cnut File Handler

Source: https://junglewise.ai/threats/cve-2026-9541-squirrel-readobject-heap-buffer-overflow-in-cnut-file-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-26. Updated: 2026-05-26  
License: CC BY 4.0 with a link back

CVE-2026-9541 · Severity: medium · CVSS 5.3 · Published 2026-05-26

Squirrel is a lightweight programming language often embedded in applications and games. A security flaw in how it handles compiled bytecode files allows a local attacker to trigger a memory corruption error. This could potentially lead to a program crash or unauthorized code execution on the affected system.

## Quick answers

**Is CVE-2026-9541 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-9541 being exploited in the wild.

**How severe is CVE-2026-9541?** Medium severity, with a CVSS score of 5.3, published 26 May 2026.

**Which products and versions are affected?** Alberto Demichelis Squirrel Up to 3.2.

**Is there a fix for CVE-2026-9541?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-9541 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-9541?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based buffer overflow exists in the ReadObject function within squirrel/sqobject.cpp of the Squirrel language (up to version 3.2). The vulnerability is caused by improper validation of string lengths read from a bytecode stream. Specifically, the ReadObject function accepts a signed SQInteger for string length without checking for negative values. When a negative length is provided, the GetScratchPad function fails to resize the buffer, but the subsequent SafeRead call passes the negative value to fread. Because fread interprets the signed integer as a large unsigned size_t, it performs an out-of-bounds write to the heap. This can be triggered by loading a malicious .cnut bytecode file via sqstd_loadfile or sq_readclosure.

## Affected products

- Alberto Demichelis Squirrel Up to 3.2

## Timeline

- 2026-04-22: disclosed: Issue reported to the project maintainer on GitHub
- 2026-05-26: advisory: CVE published by VulDB/NVD

## References

- [https://github.com/albertodemichelis/squirrel/issues/327](https://github.com/albertodemichelis/squirrel/issues/327)
- [https://github.com/biniamf/pocs/tree/main/squirrel-sqobject-readobject-neg-len-oob](https://github.com/biniamf/pocs/tree/main/squirrel-sqobject-readobject-neg-len-oob)
- [https://vuldb.com/submit/814826](https://vuldb.com/submit/814826)
- [https://vuldb.com/vuln/365602](https://vuldb.com/vuln/365602)
- [https://vuldb.com/vuln/365602/cti](https://vuldb.com/vuln/365602/cti)