CVE-2026-15747
CRITICALDescription
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 to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 17% of all known CVEs.
References
Related Vulnerabilities
Other CWE-204 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-41697 | Medium | 5.3 | 20% | - | - |
| CVE-2016-9499 | Medium | 5.3 | 7.8% | - | Fix |
| CVE-2019-19030 | Medium | 5.3 | 1.9% | - | Fix |
| CVE-2022-0564 | Medium | 5.3 | 1.4% | - | Fix |
| CVE-2021-20049 | High | 7.5 | 1.3% | - | Fix |
| CVE-2021-39189 | Medium | 5.3 | 1.3% | - | Fix |
Common questions
How do I fix CVE-2026-15747?
Upgrade libmojolicious-perl on debian unstable to 9.48+dfsg-1 or later.
Is CVE-2026-15747 being actively exploited?
Not that we know of. CVE-2026-15747 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.26% is the estimated probability that it will be exploited in the next 30 days. That is higher than 17% of all scored CVEs.
How severe is CVE-2026-15747?
CVE-2026-15747 has a CVSS v3 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-15747 affect?
Published advisories record a fix for libmojolicious-perl (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-15747
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.