{"id":"CVE-2026-27590","aliases":["GHSA-5r3v-vc8m-m96g","GO-2026-4536"],"url":"https://o3.security/vulnerability/CVE-2026-27590","summary":"Caddy: Unicode case-folding length expansion causes incorrect split_path index (SCRIPT_NAME/PATH_INFO confusion) in FastCGI transport","details":"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.","published":"2026-02-24T16:33:41.353Z","modified":"2026-08-05T03:32:28.361699755Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/caddyserver/caddy/v2","fixedVersion":"2.11.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/caddyserver/caddy/releases/tag/v2.11.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27590.json"},{"type":"ADVISORY","url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-5r3v-vc8m-m96g"},{"type":"ADVISORY","url":"https://github.com/php/frankenphp/security/advisories/GHSA-g966-83w7-6w38"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27590"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-05T03:32:28.361699755Z"}}