caddyserver caddy up to 2.11.0 path case sensitivity

Summaryinfo

A vulnerability classified as critical was found in caddyserver caddy up to 2.11.0. This impacts an unknown function. Executing a manipulation of the argument path can lead to case sensitivity. This vulnerability is registered as CVE-2026-27587. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability has been found in caddyserver caddy up to 2.11.0 and classified as critical. This vulnerability affects an unknown function. The manipulation of the argument path with an unknown input leads to a case sensitivity vulnerability. The CWE definition for the vulnerability is CWE-178. The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `path` request matcher is intended to be case-insensitive, but when the match pattern contains percent-escape sequences (`%xx`) it compares against the request's escaped path without lowercasing. An attacker can bypass path-based routing and any access controls attached to that route by changing the casing of the request path. Version 2.11.1 contains a fix for the issue.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-27587 since 02/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available.

It is declared as proof-of-concept. The vulnerability scanner Nessus provides a plugin with the ID 300054 (Linux Distros Unpatched Vulnerability : CVE-2026-27587), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.11.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (300054). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• caddyserver

Name

• caddy

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11.0

Website

• Product: https://github.com/caddyserver/caddy/

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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