Medium severity · published Sep 17, 2026
CVE-2026-77281
Caddy: rewrite placeholder re-expansion
6.5
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CA
caddy · caddyserver
< 2.11.4 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77281
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77281
github.com
https://github.com/caddyserver/caddy/commit/176b043b0104cee3f894023cd5a598ac29e404bb
github.com
https://github.com/caddyserver/caddy/pull/7761
github.com
https://github.com/caddyserver/caddy/releases/tag/v2.11.4
github.com
https://github.com/caddyserver/caddy/security/advisories/GHSA-j8px-rmrx-76h9
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