Critical severity · published Jun 15, 2020
CVE-2018-21246
Caddy before 0.10.13 mishandles TLS client authentication, as demonstrated by an authentication bypass caused by the lack of the StrictHostMatching mode
9.8
CVSS
2.7%
EPSS
No
On KEV
Description
Caddy before 0.10.13 mishandles TLS client authentication, as demonstrated by an authentication bypass caused by the lack of the StrictHostMatching mode.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)2.7% · higher than 86% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CA
Caddy · Caddyserver
before 0.10.3 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-21246
CVE.org
https://www.cve.org/CVERecord?id=CVE-2018-21246
Third Party Advisory
https://bugs.gentoo.org/715214
Release Notes
https://github.com/caddyserver/caddy/releases/tag/v0.10.13
More from Caddy
7.5
CVE-2023-44487
HTTP/2 Rapid Reset Attack Vulnerability
9.8
CVE-2026-27590
Caddy: Unicode case-folding length expansion causes incorrect split_path index (SCRIPT_NAME/PATH_INFO confusion) in FastCGI transport
9.1
CVE-2026-27588
Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass
9.1
CVE-2026-27587
Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass
9.1
CVE-2026-27586
Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed