CVE-2026-45135

Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files

State: Published
Severity: 8.1 High
Published: Jun 23, 2026
Updated: Jun 23, 2026
Reserved: May 8, 2026

Description

Caddy is an extensible server platform that uses TLS by default. From 2.7.0 until 2.11.3, the FastCGI transport's splitPos() in modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go misuses golang.org/x/text/search with search.IgnoreCase when the request path contains a non-ASCII byte. Two distinct flaws in that fallback let an attacker mislead Caddy's FastCGI splitting into treating a non-.php (or other configured split_path extension) file as a script. In any deployment where the attacker can place content into a file served via FastCGI (uploads, file storage, etc.), this can be escalated to remote code execution by crafting a URL whose path triggers either flaw. This vulnerability is fixed in 2.11.3.

Scores

CVSS	Score	Vector	Source
3.1	8.1 High	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	GitHub_M

Weaknesses

CWE-20 Improper Input Validation
CWE-176 Improper Handling of Unicode Encoding
CWE-178 Improper Handling of Case Sensitivity

Affected Products

Product	Versions
caddycaddyserver	>= 2.7.0, < 2.11.3Affected

References

https://github.com/caddyserver/caddy/security/advisories/GHSA-m675-2p33-xv9g

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