What is the CVSS score of CVE-2026-27588?

CVE-2026-27588 has a CVSS 3.1 base score of 9.1 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.0%.

Which versions of TLS are affected by CVE-2026-27588?

Caddy web servers with large host configurations (>100 entries) are vulnerable to authentication and access control bypass due to case-sensitive host matching inconsistency.. A patch is available.

Is there a public PoC exploit available for CVE-2026-27588?

Yes, a public proof-of-concept exploit is available for CVE-2026-27588. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-27588?

Within 24 hours: Inventory all Caddy deployments and identify instances with >100 host entries in configuration; implement emergency WAF rules to normalize request headers to lowercase. Within 7 days: Reduce host list entries below 100 where possible through consolidation or wildcard patterns; isolate affected Caddy instances from untrusted networks. Within 30 days: Upgrade to Caddy 2.11.1 or later when available; conduct security audit of host-based access control policies.

TLS CVE-2026-27588

CRITICAL

Improper Handling of Case Sensitivity (CWE-178)

2026-02-24 security-advisories@github.com

GHSA-x76f-jf84-rqj8

TLS Caddy Suse

9.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

9.1 CRITICAL

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

SUSE

CRITICAL

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

PoC Detected

Feb 25, 2026 - 17:10 vuln.today

Public exploit code

CVE Published

Feb 24, 2026 - 17:29 nvd

CRITICAL 9.1

DescriptionGitHub Advisory

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.

AnalysisAI

Host header case sensitivity bypass in Caddy before 2.11.1. Virtual host routing can be bypassed by using alternate casing in the Host header. PoC available.

Technical ContextAI

CWE-178 case sensitivity issue in host matching. The HTTP Host header is matched case-sensitively but DNS is case-insensitive.

RemediationAI

Update to Caddy 2.11.1.

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Same weakness CWE-178 – Improper Handling of Case Sensitivity

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Vendor StatusVendor

SUSE

Severity: Critical

Product	Status
openSUSE Leap 15.6	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP5	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP6	Fixed
openSUSE Leap 15.5	Fixed

CVE-2026-27588 vulnerability details – vuln.today

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TLS CVE-2026-27588

Severity by source

CVSS VectorGitHub Advisory

Lifecycle Timeline

DescriptionGitHub Advisory

AnalysisAI

Technical ContextAI

RemediationAI

More in TLS

Same weakness CWE-178 – Improper Handling of Case Sensitivity

Vendor StatusVendor

SUSE

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External POC / Exploit Code