CVE-2026-27588

Name: CVE-2026-27588
Creator: NVD / NIST
Published: 2026-02-24T17:29:04.163+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.7/10EPSS 0.37%

Last modified Jun 17, 2026

CVE-2026-27588 is a high-severity vulnerability rated 7.7/10 on the CVSS scale. 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. EPSS estimates a 0.37% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS 4.0

7.7/10

CVSS:4.0/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

EPSS Probability

0.37%

28.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-178

Affected Software

Vendor	Product	Versions
Caddyserver	Caddy	>= 2.10.2, < 2.11.1

References

https://github.com/caddyserver/caddy/releases/tag/v2.11.1Release Notes
https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8Exploit, Vendor Advisory

Timeline

Published: Feb 24, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-27588?

How severe is CVE-2026-27588?

CVE-2026-27588 has a CVSS score of 7.7/10 (HIGH severity). The EPSS model estimates a 0.37% probability of exploitation in the next 30 days.

How do I fix CVE-2026-27588?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-27588?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST