CVE-2026-109391: critical vulnerability in Square Squash
Square Squash through commit e73f280 Unauthenticated YAML Deserialization via Symbolication API
Published · Updated
48Vexday Risk Score
No sign of exploitation. It has a public proof of concept.
ssvc Attendcvss 9.2epss 0.5%
exploitation probability
0.5%top 60% of all CVEs
observed exploitation
nono source reports it
1 public exploit(s)
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:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected products
Square · Squashpublic PoCs found — 1
cve_referencehackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/HJ87QX5ifgunverified⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
References
https://github.com/SquareSquash/webhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/app/controllers/api/v1_controller.rbhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/app/models/symbolication.rbhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/config/preinitializers/safe_yaml.rbhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/lib/workers/symbolication_creator.rbhttps://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/HJ87QX5ifghttps://www.vulncheck.com/advisories/square-squash-through-commit-e73f280-unauthenticated-yaml-deserialization-via-symbolication-api