Executive Summary

CVE-2026-8261 is a heap-based buffer overflow vulnerability in the Squirrel scripting language up to version 3.2. It occurs in the function SQFunctionProto::Load within the file squirrel/sqobject.cpp. The issue arises due to an integer overflow in the _FUNC_SIZE macro during bytecode loading, which causes an undersized buffer allocation. Specifically, unvalidated count fields from a bytecode stream lead to a buffer that is too small, and when the program attempts to write data into this buffer, it overflows the heap.

This vulnerability can be triggered by loading a specially crafted .cnut bytecode file via functions like sqstd_loadfile or sq_readclosure. The root cause is the lack of bounds checking on count fields read from the bytecode stream, which allows an attacker to manipulate the size calculations and cause the overflow.

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Impact Analysis

This vulnerability can lead to arbitrary code execution or denial-of-service conditions if exploited. Since it is a heap buffer overflow triggered by loading crafted bytecode files, an attacker with local access could exploit this flaw to execute malicious code or crash the application using the Squirrel scripting language.

The attack is restricted to local execution, meaning remote exploitation is not indicated. However, local attackers or users who can supply malicious bytecode files could leverage this vulnerability to compromise the affected system.

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Detection Guidance

This vulnerability is triggered by loading a specially crafted .cnut bytecode file via functions like sqstd_loadfile or sq_readclosure in the Squirrel scripting language up to version 3.2.

Detection would involve identifying attempts to load suspicious or crafted .cnut files locally, as the attack is restricted to local execution.

Since the vulnerability is related to heap buffer overflow caused by integer overflow in bytecode loading, monitoring or scanning for unusual or malformed .cnut files being loaded by Squirrel processes could help.

No specific detection commands are provided in the available resources.

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Mitigation Strategies

Immediate mitigation steps include preventing the loading of untrusted or crafted .cnut bytecode files in the Squirrel environment.

Since the vulnerability is exploitable only via local execution, restricting local access to systems running vulnerable versions of Squirrel can reduce risk.

A suggested fix involves replacing the vulnerable _FUNC_SIZE macro with overflow-checked arithmetic or enforcing maximum limits on count fields immediately after reading them, but this requires patching the source code.

As the project has not yet responded with an official patch, monitoring for updates and applying patches once available is recommended.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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