Bug 2500952

Summary: CVE-2026-15747 perl-Mojolicious: Mojolicious: Information disclosure via BREACH compression oracle [epel-all]
Product: [Fedora] Fedora EPEL Reporter: Marian Rehak <mrehak>
Component: perl-MojoliciousAssignee: Emmanuel Seyman <emmanuel>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: epel10CC: emmanuel, perl-devel, robinlee.sysu, yaneti
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["e36bc75e-1724-474d-9fb7-d241f546f9e3"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2500234    

Description Marian Rehak 2026-07-15 14:17:18 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

Mojolicious versions from 4.59 before 9.48 for Perl expose a stable representation of the session CSRF token to a BREACH compression oracle.

_csrf_token generates and caches one token per session and returns the same value on every call, and _csrf_field places that value in a hidden `csrf_token` input. When a response carrying the token also echoes attacker-controlled input and is gzip-compressed, the chosen values and the resulting compressed lengths form a BREACH oracle.

An attacker able to query it can recover the token and pass csrf_protect validation.