Vulnerability · Published Jul 14, 2026 · Assigned by CPANSec
CVE-2026-15747Mojolicious versions from 4.59 before 9.48 for Perl expose a stable representation of the session CSRF token to a BREACH compression oracle
Critical 9.1
In plain English
A critical-severity cross-site request forgery in Mojolicious from SRI. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libmojolicious-perl | no fix listed | DEBIAN-CVE-2026-15747 |
| Debian:13 | libmojolicious-perl | no fix listed | DEBIAN-CVE-2026-15747 |
| Debian:14 | libmojolicious-perl | 9.48+dfsg-1 | DEBIAN-CVE-2026-15747 |
| Ubuntu:22.04:LTS | libmojolicious-perl | no fix listed | UBUNTU-CVE-2026-15747 |
| Ubuntu:24.04:LTS | libmojolicious-perl | no fix listed | UBUNTU-CVE-2026-15747 |
| Ubuntu:26.04:LTS | libmojolicious-perl | no fix listed | UBUNTU-CVE-2026-15747 |
| Ubuntu:26.10 | libmojolicious-perl | no fix listed | UBUNTU-CVE-2026-15747 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| SRI | Mojolicious | 4.59 – before 9.48 |
Weakness: CWE-204, CWE-352 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N