# CVE-2026-8258: Squirrel stack overflow in validate_format function

Source: https://junglewise.ai/threats/cve-2026-8258-squirrel-stack-overflow-in-validate-format-function  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-11. Updated: 2026-07-23  
License: CC BY 4.0 with a link back

CVE-2026-8258 · Severity: medium · CVSS 5.3 · Published 2026-05-11

A security flaw exists in the Squirrel programming language, a lightweight scripting engine used in various software and games. A local attacker can exploit this vulnerability to cause a system crash or potentially execute unauthorized code by providing specially crafted input. This could lead to a disruption of service or unauthorized access to data on the affected system.

Technologies: [Squirrel Project Squirrel](https://junglewise.ai/threats/technologies/squirrel). Vendors: [Squirrel Project](https://junglewise.ai/threats/vendors/squirrel-project).

## Quick answers

**Is CVE-2026-8258 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-8258 being exploited in the wild.

**How severe is CVE-2026-8258?** Medium severity, with a CVSS score of 5.3, published 11 May 2026.

**Which products and versions are affected?** Squirrel Project Squirrel up to 3.2.

**Is there a fix for CVE-2026-8258?** 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-2026-8258 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-8258?** Check whether you run Squirrel Project Squirrel at an affected version. 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 stack-based buffer overflow vulnerability exists in Squirrel up to version 3.2 within the 'validate_format' function of the 'sqstdlib/sqstdstring.cpp' library. The root cause is an off-by-one error during length checks when processing format strings. A local attacker with low privileges can trigger this overflow by passing a manipulated string to the affected function, potentially leading to arbitrary code execution or a denial of service. While a Proof-of-Concept (PoC) exploit has been published, the project maintainers have not yet released an official patch.

## Affected products

- Squirrel Project Squirrel up to 3.2

## Timeline

- 2026-05-11: disclosed: Vulnerability disclosed and CVE assigned
- 2026-05-11: advisory: VulDB and NVD published advisory

## References

- [https://github.com/albertodemichelis/squirrel/issues/325](https://github.com/albertodemichelis/squirrel/issues/325)
- [https://github.com/biniamf/pocs/tree/main/squirrel-validate_format-memcpy-oob](https://github.com/biniamf/pocs/tree/main/squirrel-validate_format-memcpy-oob)
- [https://vuldb.com/submit/809873](https://vuldb.com/submit/809873)
- [https://vuldb.com/vuln/362555](https://vuldb.com/vuln/362555)
- [https://vuldb.com/vuln/362555/cti](https://vuldb.com/vuln/362555/cti)

## Related threats

- [Squirrel heap buffer overflow in SQFunctionProto::Load](https://junglewise.ai/threats/cve-2026-8261-squirrel-heap-buffer-overflow-in-sqfunctionproto-load)