CVE-2018-21246: Github.com/caddyserver/caddy Authentication Bypass Vulnerability

CRITICAL
Advisory Identifier: GHSA-gr7w-x2jp-3xgw
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CVSS 9.8
CWE-287
Published
Advisory Summary

CVE-2018-21246 is a CRITICAL (CVSS 9.8) authentication bypass vulnerability (CWE-287: Improper Authentication) affecting Github.com/caddyserver/caddy libraries in the Go ecosystem. The issue involves caddy vulnerable to authentication bypass due to mishandling of tls client authentication. Remediation is available by upgrading affected packages to version 0.10.13.

CVE-2018-21246 at a Glance

CVE Identifier CVE-2018-21246
GHSA Identifier GHSA-gr7w-x2jp-3xgw
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-287: Improper Authentication
Affected Product Github.com/caddyserver/caddy
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2018-21246

To remediate this vulnerability, upgrade all affected Github.com/caddyserver/caddy dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/caddyserver/caddy fixed: 0.10.13 
Upgrade github.com/caddyserver/caddy to 0.10.13
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/caddyserver/caddy

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-21246, inspect your project dependencies for Github.com/caddyserver/caddy:

inspect dependencies for github.com/caddyserver/caddy

Analyze the terminal output to locate any version of Github.com/caddyserver/caddy in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.10.13), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Github.com/caddyserver/caddy, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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

CVE-2018-21246 Affected Github.com/caddyserver/caddy Versions

1 component(s)
Fixed Versions:
0.10.13
Product / Package Ecosystem Affected Versions Fixed Version
github.com/caddyserver/caddy
golang/github.com/caddyserver/caddy
Go
< 0.10.13
0.10.13

References

NVD — CVE-2018-21246 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-21246
Github.com/caddyserver/caddy Source Repository REPOSITORY
https://github.com/caddyserver/caddy/pull/2099
Security Fix Commit FIX COMMIT
https://github.com/caddyserver/caddy/commit/4d9ee000c8d2cbcdd8284007c1e0f2da7bc3c7c3
bugs.gentoo.org/715214 WEB
https://bugs.gentoo.org/715214
Github.com/caddyserver/caddy Source Repository REPOSITORY
https://github.com/caddyserver/caddy
Github.com/caddyserver/caddy Release RELEASE
https://github.com/caddyserver/caddy/releases/tag/v0.10.13
pkg.go.dev/vuln/go-2020-0043 WEB
https://pkg.go.dev/vuln/GO-2020-0043

Frequently Asked Questions

What is CVE-2018-21246?
CVE-2018-21246 is a security vulnerability in Github.com/caddyserver/caddy involving Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication under CWE-287: Improper Authentication.
Which Github.com/caddyserver/caddy versions are affected?
Affected versions include releases prior to 0.10.13 across affected packages: github.com/caddyserver/caddy.
What version fixes CVE-2018-21246?
Upgrading to 0.10.13 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/caddyserver/caddy affected?
Yes, github.com/caddyserver/caddy is affected in releases prior to 0.10.13. Upgrade your dependency to 0.10.13 or later.
What is the CVSS score of CVE-2018-21246?
CVE-2018-21246 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2018-21246?
CVE-2018-21246 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check Go dependencies for CVE-2018-21246?
Run the dependency tree command: 'inspect dependencies for github.com/caddyserver/caddy'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gr7w-x2jp-3xgw",
  "modified" : "2022-10-06T22:58:56Z",
  "published" : "2022-10-06T22:58:56Z",
  "aliases" : [ "CVE-2018-21246" ],
  "summary" : "Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication",
  "details" : "Caddy before 0.10.13 mishandles TLS client authentication, as demonstrated by an authentication bypass caused by the lack of the StrictHostMatching mode.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/caddyserver/caddy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.10.13"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-21246"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/caddyserver/caddy/pull/2099"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/caddyserver/caddy/commit/4d9ee000c8d2cbcdd8284007c1e0f2da7bc3c7c3"
  }, {
    "type" : "WEB",
    "url" : "https://bugs.gentoo.org/715214"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/caddyserver/caddy"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/caddyserver/caddy/releases/tag/v0.10.13"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2020-0043"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-10-06T22:58:56Z",
    "nvd_published_at" : null
  }
}