CVE-2026-77281 Caddy: rewrite placeholder re-expansion
Attackers can exploit rewrite placeholder re-expansion to disclose sensitive data and readable files if specific rewrite configurations are used.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77281?
CVE-2026-77281 is a medium-severity vulnerability in caddyserver caddy, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-77281?
How do I fix CVE-2026-77281?
Upgrade to a fixed version.
Is CVE-2026-77281 being exploited?
There is no known exploitation of CVE-2026-77281 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-77281, MINI-55pp-x7m2-gv6w, MINI-wwv5-9536-69j8, UBUNTU-CVE-2026-77281.