Code execution via class-member index confusion
Published Jul 28, 2022 · Updated May 29, 2026
Out-of-bounds read in Squirrel through 2.2.5 and 3.0 through 3.1 allows attackers to execute code via a crafted Squirrel script. SQClass::NewSlot permits enough methods to make a method index overlap the field-type bit, so Get treats it as a field index and reads beyond _defaultvalues. Execution of an attacker-controlled script is required; successful exploitation escapes the Squirrel VM sandbox and grants access to the host process.
Summary
What happened
Out-of-bounds read in Squirrel through 2.2.5 and 3.0 through 3.1 allows attackers to execute code via a crafted Squirrel script. SQClass::NewSlot permits enough methods to make a method index overlap the field-type bit, so Get treats it as a field index and reads beyond _defaultvalues. Execution of an attacker-controlled script is required; successful exploitation escapes the Squirrel VM sandbox and grants access to the host process.
The record
- CVE
- CVE-2021-41556
- Published
- Jul 28, 2022
- Updated
- May 29, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-125, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 28, 2022CVE publishedPublication date reported by the CVE source.
- May 29, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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.
Public exploit references
- Squirrel class-member index-confusion proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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