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Vulnerabilities

Vulnerability · CVE-2026-27590

Caddy is an extensible server platform that uses TLS by default.

Published Feb 24, 2026 · catalog updated Jun 17, 2026 · Caddy is an extensible

Check if you run it

No confirmed exploitation is on record for CVE-2026-27590. EPSS is 0.88%. Act only if a listed version of Caddy is an extensible is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Caddy is an extensible).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.88%
Remediation
Advisory link
Affected products
cpe caddyserver/caddy

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect / and , potentially causing a request that contains to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe caddyserver/caddyversion unspecified

How to fix CVE-2026-27590

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27590. EPSS is 0.88%. Act only if a listed version of Caddy is an extensible is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-180; CWE-20: Improper Input Validation. EPSS 0.88%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 24, 2026 · NIST NVD

    Detected

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect / and , potentially c

  2. Jun 17, 2026 · NIST NVD

    Updated

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect / and , potentially c

Sources

  • CVE.orgVulnerability recordCVE-2026-27590

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27590

    30-day exploitation probability 0.9%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27590

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode be

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.