CVE-2026-27590

caddy: Caddy is an extensible server platform that uses TLS by default

CVE-2026-27590 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-27590, released February 24, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent
CVSS
9.8
critical
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0061
49th percentile

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because `strings.ToLower()` can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect `SCRIPT_NAME`/`SCRIPT_FILENAME` and `PATH_INFO`, potentially causing a request that contains `.php` to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue.

Where it's fixed

ProductFixed inFixReleased
Linux
caddy · Debian 12.15 (bookworm) 2.6.2-5+deb12u1 DEBIAN-CVE-2026-27590 Feb 24, 2026
caddy · Debian 13.5 (trixie) 2.6.2-12+deb13u1 DEBIAN-CVE-2026-27590 Feb 24, 2026
caddy · Debian 14 2.11.2-1 DEBIAN-CVE-2026-27590 Feb 24, 2026
caddy · Fedora 43 2.10.2-9.fc43 FEDORA-2026-3DC324BD9A Jun 23, 2026
caddy-debuginfo · Fedora 43 2.10.2-9.fc43 FEDORA-2026-3DC324BD9A Jun 23, 2026
caddy-debugsource · Fedora 43 2.10.2-9.fc43 FEDORA-2026-3DC324BD9A Jun 23, 2026
govulncheck-vulndb · opensuse-leap 15.6 0.0.20260226T182644-150000.1.149.1 SUSE-SU-2026:0757-1 Mar 3, 2026
govulncheck-vulndb · opensuse-leap 16.0 0.0.20260723T184607-160000.1.1 OPENSUSE-SU-2026:21483-1 Jul 30, 2026

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