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CVE-2026-27588

Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass

No known exploitation. EPSS puts it in the 48th percentile. Fixed in 2.11.1.

CVSS 3.19.1CriticalEPSS percentile48th0.6% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix2.11.1Upgrade to this build

Published Updated Sources: CVE.org, NVD, GitHub

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • Caddyserver CaddyAffected: < 2.11.1Upgrade to: not statedStated by: CVE record
  • Go github.com/caddyserver/caddy/v2Affected: < 2.11.1Upgrade to: 2.11.1Stated by: GitHub advisory

Versions as the sources state them. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS48th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.6% chance of exploitation activity in the next 30 days, which ranks it in the 48th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

5 events over 121 days, from the signal feeds we watch.

  1. OpenVAS check added
  2. Patch availablerecord updated
  3. Publishedweakness classified

Affected products

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 9.1 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity HighTotal loss of integrity — attacker can modify any data in the component
  • Availability NoneNo availability impact

Weaknesses

Sources

References in the record

And 3 more references. See all after sign-in

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