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CVE-2026-15747

CRITICALCVSS 9.1/10EPSS 0.15%

Last modified

CVE-2026-15747 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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.. EPSS estimates a 0.15% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability
0.15%

4.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
SRIMojolicious>= 4.59, < 9.48

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-15747?
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.
How severe is CVE-2026-15747?
CVE-2026-15747 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.15% probability of exploitation in the next 30 days.
How do I fix CVE-2026-15747?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST