CVE catalog
CVE-2026-27590
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 the
- Severity
- High · CVSS 8.9
- Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.61% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | caddy | sid | 2.11.4-1 | fixed |
| Debian | caddy | forky | 2.11.4-1 | fixed |
| Debian | caddy | trixie | 2.6.2-12+deb13u1 | fixed |
| Debian | caddy | trixie-security | 2.6.2-12+deb13u1 | fixed |
| Debian | caddy | bookworm | 2.6.2-5 | vulnerable |
| Debian | caddy | bookworm-security | 2.6.2-5+deb12u1 | fixed |
| Go | github.com/caddyserver/caddy/v2/modules/caddyhttp/reverseproxy/fastcgi | Not reported | 2.11.1 | fixed |
| Cpe | caddy | Not reported | Not reported | vulnerable |
| Go | github.com/caddyserver/caddy/v2 | Not reported | 2.11.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | caddy | source | sid | 2.11.2-1 | not yet assigned | Not reported | [1132041] |
| Debian | caddy | source | forky | 2.11.2-1 | not yet assigned | Not reported | [1132041] |
| Debian | caddy | source | trixie | 2.6.2-12+deb13u1 | not yet assigned | Not reported | [1132041] |
| Debian | caddy | source | bookworm | 2.6.2-5+deb12u1 | not yet assigned | Not reported | [1132041] |
| Go | github.com/caddyserver/caddy/v2/modules/caddyhttp/reverseproxy/fastcgi | go | Not reported | 2.11.1 | Not reported | Not reported | Not reported |
| Go | github.com/caddyserver/caddy/v2 | Go | Not reported | 2.11.1 | Not reported | Not reported | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [caddy]Affected
Details (2)
2.6.2-5· amd64 · bookwormAffected · Fixed:
2.6.2-5+deb12u1nvd · caddy · debian · bookworm; nvd · caddy · debian · 12
2.6.2-5· arm64 · bookwormAffected · Fixed:
2.6.2-5+deb12u1nvd · caddy · debian · bookworm; nvd · caddy · debian · 12
[Debian 13 (Trixie)]
- [caddy]Affected
Details (5)
2.6.2-12+b3· amd64 · trixieAffected · Fixed:
2.6.2-12+deb13u1nvd · caddy · debian · 13
2.6.2-12+b3· arm64 · trixieAffected · Fixed:
2.6.2-12+deb13u1nvd · caddy · debian · 13
2.11.2-1~bpo13+1· amd64 · trixie-backportsFixed · Fixed:
2.6.2-12+deb13u1nvd · caddy · debian · 13
2.6.2-12+deb13u1· amd64 · trixie-securityFixed · Fixed:
2.6.2-12+deb13u1nvd · caddy · debian · 13
2.6.2-12+deb13u1· arm64 · trixie-securityFixed · Fixed:
2.6.2-12+deb13u1nvd · caddy · debian · 13
Observed:
References
- [https://github.com/advisories/GHSA-5r3v-vc8m-m96g]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-27590]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-27590]
- [https://pkg.go.dev/vuln/GO-2026-4536]
- [https://security-tracker.debian.org/tracker/CVE-2026-27590]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27590.json]
[Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [Go Vulnerability Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]