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CVE-2026-27588

Caddyserver Caddy vulnerability

9.1 CRITICALPublic exploitEPSS 0.54%
  1. Published24 Feb 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Caddyserver Caddy≥ 2.10.2 < 2.11.1

Remediation

Fixed in
Caddyserver Caddy≥ 2.11.1

References

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Frequently asked

Is CVE-2026-27588 being actively exploited?

CVE-2026-27588 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.54%.

How severe is CVE-2026-27588?

CVE-2026-27588 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.54% probability of exploitation.

Which products are affected by CVE-2026-27588?

Affected products include Caddyserver Caddy.

How do I fix CVE-2026-27588?

Upgrade affected software to a fixed version, for example Caddyserver Caddy 2.11.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-27588 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.