CVE-2026-27590 — Improper Input Validation in Caddy
Severity
8.9HIGHNVD
EPSS
0.3%
top 47.93%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
Timeline
PublishedFeb 24
Latest updateFeb 26
Description
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` t…
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected Packages3 packages
🔴Vulnerability Details
5OSV▶
Unicode case-folding causes incorrect split_path index in github.com/caddyserver/caddy/v2↗2026-02-26
CVEList▶
Caddy: Unicode case-folding length expansion causes incorrect split_path index (SCRIPT_NAME/PATH_INFO confusion) in FastCGI transport↗2026-02-24
OSV▶
Caddy: Unicode case-folding length expansion causes incorrect split_path index in FastCGI transport↗2026-02-24
GHSA▶
Caddy: Unicode case-folding length expansion causes incorrect split_path index in FastCGI transport↗2026-02-24
📋Vendor Advisories
1Debian▶
CVE-2026-27590: caddy - Caddy is an extensible server platform that uses TLS by default. Prior to versio...↗2026