CVE-2026-109391: Deserialization of Untrusted Data in Square Squash
Description
Square Squash through commit e73f280 contains an insecure deserialization vulnerability that allows unauthenticated attackers to store crafted YAML via the POST /api/1.0/symbolication endpoint. When occurrences referencing the attacker-controlled symbolication UUID are symbolicated, the stored values are passed to YAML.load with SafeYAML in unsafe mode, enabling arbitrary Ruby object deserialization and potential code execution.
CVSS v4.0
Score 9.2critical
Affected software
Square
Squash
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Square Squash, as of commit e73f280, contains an insecure deserialization vulnerability in the POST /api/1.0/symbolication endpoint. Attackers can store malicious YAML referencing a symbolication UUID they control. When these occurrences are processed, the stored YAML is deserialized using YAML.load with SafeYAML in unsafe mode, which permits arbitrary Ruby object deserialization and can lead to code execution. The vulnerability is unauthenticated and has a high CVSS 4.0 score of 9.2, indicating critical severity.
Potential Impact
An unauthenticated attacker can exploit this vulnerability to execute arbitrary code on the affected system by sending crafted YAML data to the symbolication API endpoint. This could lead to full system compromise depending on the privileges of the application process.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided. Until a patch is available, restrict access to the vulnerable endpoint and monitor for suspicious activity related to symbolication requests.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-10-12T14:40:37.988Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6accfdf32cdf04f656a88558
Added to database: 10/12/2026, 15:34:11 UTC
Last enriched: 10/12/2026, 15:48:26 UTC
Last updated: 10/12/2026, 21:47:05 UTC
Views: 12
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