CVE-2026-77281— Caddy: rewrite placeholder re-expansion
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.
Caddy 是一个可扩展的服务器平台，默认使用 TLS。在 2.11.3 及更早版本中，三个与配置相关的弱点影响了处理程序和占位符层。在 中，当重写 URI 以字面问号结尾时， 会将攻击者控制的替换字节传递到 进行第二次占位符扩展，从而允许注入的环境变量或请求变量占位符泄露数据；当注册了文件提供程序时，注入的文件占位符还可泄露可读文件内容。该问题已在 2.11.4 版本中修复。
Possible ATT&CK Techniques 2 AI
T1190 · Exploit Public-Facing Application T1505 · Server Software Component
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I. Basic Information for CVE-2026-77281
Vulnerability Information
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Vulnerability Title
Caddy: rewrite placeholder re-expansion
Source: CVE Program / CVE List V5
Vulnerability Description
Caddy is an extensible server platform that uses TLS by default. In version 2.11.3 and earlier, three configuration-dependent weaknesses affect the handler and placeholder layer. In modules/caddyhttp/rewrite/rewrite.go, Rewrite.Rewrite() can pass attacker-controlled replacement bytes through buildQueryString for a second placeholder expansion when a rewrite URI ends with a literal question mark, allowing injected environment or request-variable placeholders to disclose data and, when the file provider is registered, allowing injected file placeholders to disclose readable files. The issue is fixed in version 2.11.4.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| caddyserver | caddy | < 2.11.4 | - |
|
II. Public POCs for CVE-2026-77281
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-77281 (2)
Vendor Advisories for CVE-2026-77281 (1)
Vendor Pages for CVE-2026-77281 (1)
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Same weakness: CWE-94
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V. Comments for CVE-2026-77281
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