CVE-2026-27590 Details
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.
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Exploit prediction scoring system (EPSS) score for CVE-2026-27590
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.19 Probability of exploitation activity being observed over the next 30 days (41st percentile)
CVSS score for CVE-2026-27590
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
9.8 Critical
Products affected by CVE-2026-27590
Caddy 0.11.1
Caddy 2.7.6
Caddy 2.4.6
Caddy 2.8.4
Caddy 2.7.5
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
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CVE-2026-27590 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
PL 888 46.54%
CN 336 17.61%
HU 197 10.32%
US 171 8.96%
DE 58 3.04%
GB 52 2.73%
SG 48 2.52%
SK 33 1.73%
PS 17 0.89%
IT 16 0.84%

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CVE-2026-27590 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 571 83.24%
Telecommunications 113 16.47%
Media/Entertainment 1 0.15%
Manufacturing 1 0.15%

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