CVE-2018-21246 is a critical-severity (CVSS 9.8) Improper Authentication vulnerability in github.com/caddyserver/caddy. A fix is available for github.com/caddyserver/caddy — see the affected versions and patch details below.
Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/caddyserver/caddyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Caddy before 0.10.13 mishandles TLS client authentication, as demonstrated by an authentication bypass caused by the lack of the StrictHostMatching mode.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/caddyserver/caddy | all versions | 0.10.13go get github.com/caddyserver/caddy@v0.10.13 |
Affected Products
caddycaddyserverDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/caddyserver/caddy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/caddyserver/caddy to 0.10.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-21246 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2018-21246 in your dependencies?
Find it across Go, including transitive dependencies.