Bug 2491908 (CVE-2026-52846)

Summary: CVE-2026-52846 github.com/caddyserver/caddy: Caddy: Client-side Cross-Site Scripting (XSS) due to incomplete HTML tag stripping
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abuckta, aprice, cmah, crizzo, dkuc, eshamard, gtanzill, jbuscemi, jdobes, jmitchel, jsamir, jsherril, jvasik, kaycoth, kgaikwad, kshier, mstipich, oezr, orabin, rblanco, rexwhite, rochandr, stcannon, sthirugn, teagle, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Caddy, an extensible server platform. The `stripHTML` template function, intended to remove HTML tags from input, fails to reliably process certain malformed HTML. This oversight allows dangerous content to remain in the output, which, if subsequently rendered as HTML, can lead to client-side Cross-Site Scripting (XSS). A remote attacker could exploit this by providing specially crafted input, potentially executing malicious scripts in a user's browser.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2499696, 2499697    
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Description OSIDB Bzimport 2026-06-23 19:02:50 UTC
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.