Local code execution via bytecode count overflow
Published May 11, 2026 · Updated May 11, 2026
Heap-based buffer overflow in SQFunctionProto::Load in Squirrel 3.0 through 3.2 allows local users to crash or execute code via crafted bytecode. The loader accepts unvalidated nlineinfos and ndefaultparams counts, lets _FUNC_SIZE wrap to a roughly 248-byte allocation, then SafeRead writes the declared line-info data past that heap buffer. Exploitation requires a 64-bit Squirrel runtime or embedding application to load attacker-supplied .cnut bytecode; the demonstrated consequence is a process crash, while the overwritten content supports code execution.
Summary
What happened
Heap-based buffer overflow in SQFunctionProto::Load in Squirrel 3.0 through 3.2 allows local users to crash or execute code via crafted bytecode. The loader accepts unvalidated nlineinfos and ndefaultparams counts, lets _FUNC_SIZE wrap to a roughly 248-byte allocation, then SafeRead writes the declared line-info data past that heap buffer. Exploitation requires a 64-bit Squirrel runtime or embedding application to load attacker-supplied .cnut bytecode; the demonstrated consequence is a process crash, while the overwritten content supports code execution.
The record
- CVE
- CVE-2026-8261
- Published
- May 11, 2026
- Updated
- May 11, 2026
- Vendor
- Squirrel
- Product
- Squirrel
- Classifications
- CWE-122, CWE-119, CAPEC-92, T1203
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 11, 2026CVE publishedPublication date reported by the CVE source.
- May 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.0
- Affected versionversion=3.1
- Affected versionversion=3.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Crafted Squirrel bytecode proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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