CVE-2026-52846: caddyserver caddy Improper Encoding or Escaping of Output

Vulnerability summary

CVE-2026-52846 is a medium (CVSS 4.2) Improper Encoding or Escaping of Output vulnerability in caddyserver caddy. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.1% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 23-06-2026
   PublishedVulnerability first disclosed.
2. 25-06-2026
   Last modifiedVulnerability information updated.

Description

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, Caddy’s stripHTML template function cannot reliably remove all HTML tags from input strings. Certain malformed HTML, such as <<>img src=x onerror=alert()>, can bypass the tag-stripping logic, potentially leaving dangerous content in the output if it is later rendered as HTML. This may allow client-side XSS in cases where untrusted strings are rendered unsafely. This vulnerability is fixed in 2.11.4.

• CWE-116Improper Encoding or Escaping of OutputThe product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.