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A GitHub-reviewed security advisory, not necessarily under active exploitation the way our CISA KEV advisories are, but a real, disclosed vulnerability in an open-source dependency.
Affected packages
Vulnerable: < 1.12.1
Patched in 1.12.1
Details
Morgan writes attacker-controlled request data to the access log. Its escaping (added in 1.11.0 and 1.12.0) neutralizes control characters, the Unicode line separators, and backslash, but not the double quote (0x22), which is the field delimiter of the Apache combined log format morgan emits. An attacker who controls a quoted field (:user-agent, :referrer, the request URL, or the Basic auth :remote-user) can inject a double quote to close the field early and forge additional fields in the log record. The combined, common, and default formats, and any custom format that quotes a token, are affected. This is an incomplete fix of CVE-2026-5078 and CVE-2026-15603.
Users should upgrade to version 1.12.1.
Update to version 1.12.1.
EPSS, exploit probability
Low0.41%
estimated chance of real-world exploitation in the next 30 days, higher than 35.8% of every CVE FIRST.org scores
Refreshed 11/13/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.
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