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TI-2026-71027 Aliases CVE-2026-109391GHSA-f7j3-hchq-qp35

Insecure YAML deserialization in Square Squash symbolication API

Priority MEDIUM 42CWE-502Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Attack requirements
Present
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-502.

Summary

Square Squash through commit e73f280 deserializes untrusted data without checks (CWE-502). An unauthenticated remote attacker can store crafted YAML through the POST /api/1.0/symbolication endpoint, and it is loaded in unsafe mode during symbolication, enabling arbitrary Ruby object deserialization and potential code execution. A public exploit is linked in the references.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00477 41st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by the CNA
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

No affected products listed by the sources yet.

Remediation

The sources list no fixed version for Square Squash.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Timeline

  1. 2026-10-12 Threatist record created from CVE-2026-109391
  2. 2026-10-12 Alias added: GHSA-f7j3-hchq-qp35
  3. 2026-10-13 CISA SSVC decision points changed

References

Exploit 1

Other 5

  • TI-2026-45064 Integer overflow in square wire CVSS 3.1HIGH 7.5
  • TI-2026-44167 Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service CVSS 3.1HIGH 7.5
  • TI-2024-38317 Uncontrolled recursion in square Wire CVSS 3.1MEDIUM 5.8

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences