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

Quick assessment

Affected
caddyserver caddy
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

caddyserver caddy是caddyserver团队开源的一款Web服务器软件。 caddyserver caddy 2.11.4之前版本存在输出处理不当漏洞，该漏洞源于stripHTML模板函数无法可靠移除所有HTML标签，某些畸形HTML可绕过标签剥离逻辑，可能导致客户端跨站脚本攻击。

CVSS 4.2 · Medium EPSS 0.19% · P9

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise

Affected Version Matrix 1

VendorProduct Version RangeStatus
caddyserver caddy < 2.11.4 affected
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I. Basic Information for CVE-2026-52846

Vulnerability Information
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Vulnerability Title
Caddy: stripHTML template function bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
caddyserver caddy 输出处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
caddyserver caddy是caddyserver团队开源的一款Web服务器软件。 caddyserver caddy 2.11.4之前版本存在输出处理不当漏洞，该漏洞源于stripHTML模板函数无法可靠移除所有HTML标签，某些畸形HTML可绕过标签剥离逻辑，可能导致客户端跨站脚本攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
caddyserver caddy < 2.11.4 -

II. Public POCs for CVE-2026-52846

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III. Intelligence Information for CVE-2026-52846

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Vendor Advisories for CVE-2026-52846 (1)

Same Patch Batch · caddyserver · 2026-06-23 · 5 CVEs total

CVE-2026-45135 8.1 HIGH Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files
CVE-2026-52845 8.1 HIGH Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`
CVE-2026-52844 7.5 HIGH Caddy: Windows `file_server` path authorization bypass via encoded backslash
CVE-2026-45692 5.4 MEDIUM Caddy: Remote Admin Authorization Bypass in `/config` API via Array Index Normalization

IV. Related Vulnerabilities

Same product: caddy
Same vendor: caddyserver
Same weakness: CWE-116

V. Comments for CVE-2026-52846

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