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CVE-2022-23632

Traefik skips the router TLS configuration when the host header is an FQDN

7.4 HighFix available

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.6.1, Traefik skips the router transport layer security (TLS) configuration when the host header is a fully qualified domain name (FQDN). For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration. When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one. If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration. Version 2.6.1 contains a patch for this issue. As a workaround, one may add the FDQN to the host rule. However, there is no workaround if the CNAME flattening is enabled.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

1.71%Up 0.8 points since Feb 18, 2022
90%50%10%1%

What each source reports

CVE List Score used 7.4

Traefik skips the router TLS configuration when the host header is an FQDN

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.6.1, Traefik skips the router transport layer security (TLS) configuration when the host header is a fully qualified domain name (FQDN). For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration. When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one. If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration. Version 2.6.1 contains a patch for this issue. As a workaround, one may add the FDQN to the host rule. However, there is no workaround if the CNAME flattening is enabled.

Record
CVE-2022-23632
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295
Updated
2026-11-02
EUVDEUVD-2022-1054 7.4

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.6.1, Traefik skips the router transport layer security (TLS) configuration when the host header is a fully qualified domain name (FQDN). For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration. When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one. If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration. Version 2.6.1 contains a patch for this issue. As a workaround, one may add the FDQN to the host rule. However, there is no workaround if the CNAME flattening is enabled.

Record
EUVD-2022-1054
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-hrhx-6h34-j5hc 7.4

Skip the router TLS configuration when the host header is an FQDN

Impact

People that configure mTLS between Traefik and clients.

For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration.

  • When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one.

  • If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration.

Patches

Traefik v2.6.x: https://github.com/traefik/traefik/releases/tag/v2.6.1

Workarounds

Add the FDQN to the host rule:

Example:

  whoami:
    image: traefik/whoami:v1.7.1
    labels:
      traefik.http.routers.whoami.rule: Host(`whoami.example.com`, `whoami.example.com.`)
      traefik.http.routers.whoami.tls: true
      traefik.http.routers.whoami.tls.options: mtls@file

There is no workaround if the CNAME flattening is enabled.

For more information

If you have any questions or comments about this advisory, please open an issue.

Record
GHSA-hrhx-6h34-j5hc
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295
Updated
2026-11-02
NVD 7.4

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.6.1, Traefik skips the router transport layer security (TLS) configuration when the host header is a fully qualified domain name (FQDN). For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration. When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one. If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration. Version 2.6.1 contains a patch for this issue. As a workaround, one may add the FDQN to the host rule. However, there is no workaround if the CNAME flattening is enabled.

Record
CVE-2022-23632
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 2.0
6.8 MediumAV:N/AC:M/Au:N/C:P/I:P/A:P
Weakness
CWE-295
Updated
2026-11-02
OSV 7.4

Traefik skips the router TLS configuration when the host header is an FQDN

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.6.1, Traefik skips the router transport layer security (TLS) configuration when the host header is a fully qualified domain name (FQDN). For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration. When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one. If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration. Version 2.6.1 contains a patch for this issue. As a workaround, one may add the FDQN to the host rule. However, there is no workaround if the CNAME flattening is enabled.

Record
CVE-2022-23632
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295
Updated
2026-11-02
OSVGHSA-hrhx-6h34-j5hc 7.4

Skip the router TLS configuration when the host header is an FQDN

Impact

People that configure mTLS between Traefik and clients.

For a request, the TLS configuration choice can be different than the router choice, which implies the use of a wrong TLS configuration.

  • When sending a request using FQDN handled by a router configured with a dedicated TLS configuration, the TLS configuration falls back to the default configuration that might not correspond to the configured one.

  • If the CNAME flattening is enabled, the selected TLS configuration is the SNI one and the routing uses the CNAME value, so this can skip the expected TLS configuration.

Patches

Traefik v2.6.x: https://github.com/traefik/traefik/releases/tag/v2.6.1

Workarounds

Add the FDQN to the host rule:

Example:

  whoami:
    image: traefik/whoami:v1.7.1
    labels:
      traefik.http.routers.whoami.rule: Host(`whoami.example.com`, `whoami.example.com.`)
      traefik.http.routers.whoami.tls: true
      traefik.http.routers.whoami.tls.options: mtls@file

There is no workaround if the CNAME flattening is enabled.

For more information

If you have any questions or comments about this advisory, please open an issue.

Record
GHSA-hrhx-6h34-j5hc
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295
Updated
2026-11-02
OSVGO-2022-0325 No score

Skip the router TLS configuration when the host header is an FQDN in github.com/traefik/traefik

Skip the router TLS configuration when the host header is an FQDN in github.com/traefik/traefik

Record
GO-2022-0325
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/traefik/traefik/v2
Go
 before 2.6.1
2.6.1
github.com/traefik/traefik
Go
 All versions None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2022-23632 is a high vulnerability (CVSS 7.4) in Traefik, published February 16, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.71%, the 77th percentile. Fixed in github.com/traefik/traefik/v2 2.6.1.

References

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