CVE-2026-27590
9.8 · CRITICALOverview
CVE-2026-27590 is a critical-severity vulnerability affecting caddyserver caddy. It was published on February 24, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from caddyserver. Update caddy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| caddyserver | caddy | >= 0, < 2.11.1 | Affected |
Frequently Asked Questions
What is CVE-2026-27590?
CVE-2026-27590 is a critical-severity vulnerability affecting caddyserver caddy. It was published on February 24, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).
How severe is CVE-2026-27590?
This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-27590?
Check the references section for vendor advisories and patches from caddyserver. Update caddy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-27590?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-27590 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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