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

CVE-2026-27590 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.2%.

Which versions of PHP are affected by CVE-2026-27590?

A critical vulnerability in Caddy web servers (CVE-2026-27590, CVSS 9.8) enables attackers to bypass security controls and execute arbitrary code through malformed FastCGI requests.. A patch is available.

Is there a public PoC exploit available for CVE-2026-27590?

Yes, a public proof-of-concept exploit is available for CVE-2026-27590. Prioritise patching immediately. EPSS: 0.2%.

How to fix or mitigate CVE-2026-27590?

Within 24 hours: Identify all Caddy instances in production and their versions; disable FastCGI functionality if not essential or restrict access via network segmentation. Within 7 days: Deploy compensating controls (WAF rules blocking malicious path patterns, API gateway filtering); establish monitoring for exploitation attempts. Within 30 days: Upgrade to Caddy 2.11.1 or later once patch availability is confirmed; conduct forensic review of logs for potential compromise indicators.

PHP CVE-2026-27590

CRITICAL

Improper Input Validation (CWE-20)

2026-02-24 security-advisories@github.com

GHSA-5r3v-vc8m-m96g

PHP TLS RCE Caddy Suse

9.8

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

9.8 CRITICAL

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

SUSE

CRITICAL

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

PoC Detected

Feb 25, 2026 - 17:07 vuln.today

Public exploit code

CVE Published

Feb 24, 2026 - 17:29 nvd

CRITICAL 9.8

DescriptionGitHub Advisory

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.

AnalysisAI

FastCGI path splitting vulnerability in Caddy before 2.11.1 allows request smuggling or path confusion when proxying to FastCGI backends (PHP-FPM). EPSS 0.19% with PoC available.

Technical ContextAI

CWE-20 in Caddy's FastCGI reverse proxy. Path splitting allows manipulating SCRIPT_NAME/PATH_INFO splitting sent to PHP-FPM, enabling access to unintended PHP scripts.

RemediationAI

Update to Caddy 2.11.1.

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Vendor StatusVendor

SUSE

Severity: Critical

Product	Status
openSUSE Leap 15.6	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP5	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP6	Fixed
openSUSE Leap 15.5	Fixed

CVE-2026-27590 vulnerability details – vuln.today

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PHP CVE-2026-27590

Severity by source

CVSS VectorGitHub Advisory

Lifecycle Timeline

DescriptionGitHub Advisory

AnalysisAI

Technical ContextAI

RemediationAI

More in PHP

Same weakness CWE-20 – Improper Input Validation

Same technique RCE

Vendor StatusVendor

SUSE

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External POC / Exploit Code