CVE-2026-52846: Caddy: stripHTML template function bypass

Severity: medium (CVSS 4.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-23 · updated 2026-06-29
Weakness: CWE-116

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.

Affected products

caddyserver caddy: before 2.11.4 — fixed in 2.11.4

How to fix

Upgrade to a fixed version: caddyserver caddy 2.11.4. Check the vendor advisory for mitigations.

References

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