CVE-2026-52846
MediumCVSS 4.2Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
Caddy before version 2.11.4 has a vulnerability in the stripHTML template function that cannot reliably remove all HTML tags from input strings. Malformed HTML, such as <<>img src=x onerror=alert()>, can bypass the tag-stripping logic, potentially leaving dangerous content in the output.
Risk Assessment
The risk involves potential client-side XSS attacks if untrusted strings are later rendered as HTML. This could lead to session data theft, user account takeover, or malicious code execution in the victim's browser.
Recommendation
Immediately update Caddy to version 2.11.4 or later, which includes the fix for this vulnerability. Additionally, avoid rendering untrusted input as HTML without proper sanitization.
Other vulnerabilities in Caddy
See all- CVE-2026-52845High
Caddy before version 2.11.4 has a vulnerability in the forward_auth copy_headers mechanism that allows a remote client to bypass identity header deletion and inject its own header into CGI/PHP-FastCGI. The issue arises from a difference in HTTP header normalization (replacing hyphens with underscores) between Caddy and PHP/FastCGI.
- CVE-2026-52844High
Caddy before version 2.11.4 on Windows incorrectly handles path separators in path matchers, allowing bypass of access controls to protected directories. An unauthenticated remote attacker can access protected resources.
Original NVD description (English source)
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.