CVE-2026-27588
Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass
Description
Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.
INFO
Published Date :
Feb. 24, 2026, 5:29 p.m.
Last Modified :
Feb. 25, 2026, 5:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Caddy to version 2.11.1 or later.
- Verify host matching behavior.
- Review access control configurations.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27588.
| URL | Resource |
|---|---|
| https://github.com/caddyserver/caddy/releases/tag/v2.11.1 | Release Notes |
| https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8 | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27588 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27588
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27588 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27588 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Feb. 25, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Added CPE Configuration OR *cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:* versions from (including) 2.10.2 up to (excluding) 2.11.1 Added Reference Type GitHub, Inc.: https://github.com/caddyserver/caddy/releases/tag/v2.11.1 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8 Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Feb. 24, 2026
Action Type Old Value New Value Added Description Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-178 Added Reference https://github.com/caddyserver/caddy/releases/tag/v2.11.1 Added Reference https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8