CVE-2026-109391

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

• ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.47% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 40.9% of scored records. A rank, not a probability.

NVD base score

9.2 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD analysis status

Deferred. NVD last modified this record on 2026-10-16.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-10-12 15:16Z16 DAYS AGO

Last updated

2026-10-27 01:30Z2 DAYS AGO

Reserved

2026-10-12

Assigning CNA

VulnCheck

Record state

PUBLISHED

Severity

Critical (CVSS 9.2)

CNA CVSS vector

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

Weaknesses

• CWE-502Deserialization of Untrusted DataBase

Data version

5.2

Document digest

c2aee794405564b9b7d56a4c775939a2858b44577cfac29d89d5323308ecbd89

• hackmd.ioResearcher Disclosurehttps://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/HJ87QX5ifgtechnical-descriptionexploit
• github.comhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/app/controllers/api/v1_controller.rbtechnical-description
• github.comhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/config/preinitializers/safe_yaml.rbtechnical-description
• github.comhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/lib/workers/symbolication_creator.rbtechnical-description
• github.comhttps://github.com/SquareSquash/web/blob/e73f2805f9eb30780a5c213b001f0f4255660fbf/app/models/symbolication.rbtechnical-description
• github.comhttps://github.com/SquareSquash/webproduct
• www.vulncheck.comVulnCheck Advisory: Square Squash through commit e73f280 Unauthenticated YAML Deserialization via Symbolication APIhttps://www.vulncheck.com/advisories/square-squash-through-commit-e73f280-unauthenticated-yaml-deserialization-via-symbolication-apithird-party-advisory