What is CVE-2026-27590?

CVE-2026-27590 is a critical-severity vulnerability in Caddyserver Caddy, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2026-02-24.

How severe is CVE-2026-27590?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Improper input validation in Caddyserver Caddy

CVE-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 ori…

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

EPSS: 0.005 (42.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Caddyserver Caddy — versions < 2.11.1

Weakness classification (CWE)

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (Third Party Advisory, x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC, Release Notes)

Frequently asked questions

What is CVE-2026-27590?: CVE-2026-27590 is a critical-severity vulnerability in Caddyserver Caddy, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2026-02-24.
How severe is CVE-2026-27590?: Critical severity. CVSS v3 base score is 9.8 out of 10.