Is CVE-2026-27590 in the CISA KEV catalog?

No. CVE-2026-27590 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-27590?

CVE-2026-27590 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2026-27590?

CVE-2026-27590 has an EPSS score of 0.54% (42th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27590?

Upgrade caddy on debian unstable to 2.11.2-1 or later.

CVE & CISA-KEV Catalog

CVE-2026-27590

CRITICAL

9.8

CVSS v3

NVD

Description

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 `strings.ToLower()` can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect `SCRIPT_NAME`/`SCRIPT_FILENAME` and `PATH_INFO`, potentially causing a request that contains `.php` 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.

CWE-20Improper Input Validation CWE-180

How to fix

Remediation Available

caddyDebian

Fixed in:2.11.2-1CVE-2026-27590

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.54%probability of exploitation in 30 days

42ndpercentile

Moderate risk: more likely to be exploited than 42% of all known CVEs.

References

Exploit1

github.com

Third-Party Advisory1

github.com

Release Notes1

github.com

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	Fix

Embed a live status badge for CVE-2026-27590

Markdown

[![CVE-2026-27590](https://tridentstack.com/cve/badge/CVE-2026-27590.svg)](https://tridentstack.com/cve/CVE-2026-27590)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-27590"><img src="https://tridentstack.com/cve/badge/CVE-2026-27590.svg" alt="CVE-2026-27590"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-25.