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Fencer Intel
critical 9.8

CVE-2018-21246 json

Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication

published 6y ago modified 4mo ago also GHSA-gr7w-x2jp-3xgw , GO-2020-0043 , EUVD-2022-7098

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.7%
EPSS 2.7% chance of exploitation in 30 days, percentile 86%
public exploits
0
none known

Summary

Caddy before 0.10.13 mishandles TLS client authentication, as demonstrated by an authentication bypass caused by the lack of the StrictHostMatching mode.

Patch / fix

  • go github.com/caddyserver/caddy 0.10.13
  • go github.com/mholt/caddy 0.10.13
  • caddyserver caddy 0.10.3

Is CVE-2018-21246 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-21246 updated cvss 7.4

caddy: Does not have tls StrictHostMatching mode enabled which could result in client auth bypass

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.72% chance of exploitation in the next 30 days, higher than 86% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
go github.com/caddyserver/caddy
<0.10.13
0.10.13
go github.com/mholt/caddy
<0.10.13
0.10.13

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.