Description
Caddy is an extensible server platform that uses TLS by default. From version 2.7.5 to before version 2.11.2, the vars_regexp matcher in vars.go:337 double-expands user-controlled input through the Caddy replacer. When vars_regexp matches against a placeholder like {http.request.header.X-Input}, the header value gets resolved once (expected), then passed through repl.ReplaceAll() again (the bug). This means an attacker can put {env.DATABASE_URL} or {file./etc/passwd} in a request header and the server will evaluate it, leaking environment variables, file contents, and system info. This issue has been patched in version 2.11.2.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| caddyserver | caddy | >= 2.7.5, < 2.11.2 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | caddy | No fix yet | — |
| Ubuntu 25.10 | caddy | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | caddy | No fix yet | — |
| Ubuntu Pro 24.04 LTS | caddy | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 | openSUSE-SU-2026:21483-1 |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20260317T205859-150000.1.152.1 | SUSE-SU-2026:1042-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | caddy | 2.11.2-r0 | — |
| Alpine v3.23 | caddy | 2.11.2-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/caddyserver/caddy/v2 | >= 2.7.5, < 2.11.2 | 2.11.2 | GO-2026-4644 |
| Go | github.com/caddyserver/caddy/v2/modules/caddyhttp | >= 2.7.5, < 2.11.2 | 2.11.2 | GHSA-m2w3-8f23-hxxf |
Advisories 2
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:1042-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 26, 2026