9.2

CVE-2026-109391: Square Squash through commit e73f280 Unauthenticated YAML Deserialization via Symbolication API

Deferred
Published 12-10-2026Last modified 27-10-2026

Vulnerability summary

CVE-2026-109391 is a critical (CVSS 9.2) Deserialization of Untrusted Data vulnerability in square squash. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 41.3% of scored vulnerabilities. 1 public exploit is recorded.

Priority
Prioritisepublic exploit

Public exploit (reference, Date unknown)

Source freshness unavailable

How is this decided?
CVSS score
9.2/10
010
Critical · v4.0 (NVD)
EPSS score
0.48%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits1reference

Timeline

  1. 12-10-2026
    PublishedVulnerability first disclosed.
  2. 27-10-2026
    Last modifiedVulnerability information updated.

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 metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.48%

Chance of exploitation in the next 30 days

Percentile

41%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

13-10-202604-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

1 found
  • referenceUnverified

    Exploit Reference (hackmd.io)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Square1 product
  • squash≤ e73f2805f9eb30780a5c213b001f0f4255660fbf

1 vendor · 1 product

References

7 links