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TI-2026-23681 Aliases CVE-2026-30852GHSA-m2w3-8f23-hxxf

Caddy: vars_regexp double-expands user input, leaking env vars and files

Priority MEDIUM 64CWE-200Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-200.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00466 40th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed caddy (caddyserver): 2.11.2github.com/caddyserver/caddy/v2/modules/caddyhttp (Go): 2.11.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
caddyservercaddy2.7.5 to before 2.11.22.11.2Patch availableCNA
—github.com/caddyserver/caddy/v2/modules/caddyhttp (Go)2.7.5 to before 2.11.22.11.2Patch availableGHSA-m2w3-8f23-hxxf
  • caddy Vendorcaddyserver Affected 2.7.5 to before 2.11.2 Fixed in 2.11.2 Patch available CNA
  • github.com/caddyserver/caddy/v2/modules/caddyhttp (Go) Vendor— Affected 2.7.5 to before 2.11.2 Fixed in 2.11.2 Patch available GHSA-m2w3-8f23-hxxf

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*2.7.5 to before 2.11.2Vulnerablecaddyserver
  • cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:* Versions 2.7.5 to before 2.11.2 Vulnerable ·caddyserver

Remediation

  • Fix · CNA caddy (caddyserver) Fixed in 2.11.2
  • Fix · GHSA-m2w3-8f23-hxxf github.com/caddyserver/caddy/v2/modules/caddyhttp (Go) Fixed in 2.11.2 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-30852
  2. 2026-10-03 Alias added: GHSA-m2w3-8f23-hxxf

References

Exploit 1

Patch 1

Advisory 1

Other 2

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2026-21978 Improper input validation in caddyserver caddy CVSS 4.0HIGH 8.9
  • TI-2026-21974 Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed CVSS 4.0HIGH 8.8
  • TI-2026-23680 Improper authentication in caddyserver caddy CVSS 3.1HIGH 8.8
  • TI-2026-21976 Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass CVSS 4.0HIGH 7.7
  • TI-2026-21975 Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass CVSS 4.0HIGH 7.7
See all 19 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences