CVE-2026-15747

Critical

Description

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.

SeverityCritical

CVSS9.1

Exploit probability—

Product

Mojolicious

PublishedJul 14, 2026

First seenJul 14, 2026

Weakness typeCWE-204CWE-204 CWE-352Cross-site request forgery (CSRF)

How to fix

Update

SRI Mojolicious9.48 or later

Patches

github.com/mojolicious/mojo/commit/01921fbbbbeca2d1397e082d4a647f9b84c24e27.patch

Vendor advisories

metacpan.org/release/SRI/Mojolicious-9.48/changes

Affected products

Product	Affected versions	Fixed in
SRI Mojolicious	4.59 ≤ v < 9.48	9.48

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