CVE-2019-20894: Improper Authentication in Traefik 2.x
Summary
CVE-2019-20894: Improper Authentication. Affects github.com/traefik/traefik/v2 versions < 2.2.2. Fixed in 2.2.2. How to fix ↓
Also tracked for
The same CVE-2019-20894 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Traefik is a popular reverse proxy and load balancer that is written in Go. It is designed to help developers easily deploy microservices and manage web applications. Traefik 2.x is a specific version of Traefik that introduced new features and improvements. However, in certain configurations, Traefik 2.x is vulnerable to an improper authentication issue.
Vulnerability Detail
The vulnerability (CVE-2019-20894) in Traefik 2.x allows HTTPS sessions to proceed without mutual TLS verification, even when it should have been enforced. This means that an attacker can establish a connection to the server without providing a valid client certificate, bypassing the expected authentication process. This can lead to unauthorized access and potential security breaches. The vulnerability has a CVSS score of 7.5, indicating a high severity level.
How To Fix
Latest published version: v2.11.60 as of 22 Oct 2026
go get github.com/traefik/traefik/v2@v2.11.60Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
2.2.2
This is the first release that contains the fix.
go get github.com/traefik/traefik/v2@v2.2.2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading Traefik is not immediately feasible, you can implement a workaround to mitigate the risk. One possible workaround is to configure Traefik to enforce mutual TLS verification by explicitly specifying the required client certificates. This can be done by modifying the Traefik configuration file to include the necessary TLS options. Here's an example of how the configuration snippet may look:
[entryPoints]
[entryPoints.web]
address = ":443"
[entryPoints.web.tls]
clientCAFiles = ["/path/to/client-certs.pem"]
clientAuth = "RequireAndVerifyClientCert"
By specifying the clientCAFiles option with the path to the client certificates file and setting clientAuth to "RequireAndVerifyClientCert", Traefik will enforce mutual TLS verification.
Conclusion
In conclusion, the CVE-2019-20894 vulnerability in Traefik 2.x allows for improper authentication, potentially leading to unauthorized access. It is crucial to upgrade Traefik to version 2.2.2 or later to fix this vulnerability. If immediate upgrade is not possible, implementing a workaround to enforce mutual TLS verification can help mitigate the risk. For further support and assistance with vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for github.com/traefik/traefik/v2 →
FAQ
Traefik is a reverse proxy and load balancer that helps developers deploy and manage web applications and microservices.
The vulnerability allows HTTPS sessions to proceed without proper authentication, potentially leading to unauthorized access and security breaches.
The CVSS score of this vulnerability is 7.5, indicating a high severity level.
To fix this vulnerability, upgrade Traefik to version 2.2.2 or later. Alternatively, you can implement a workaround by configuring Traefik to enforce mutual TLS verification.
You can find more information about this vulnerability in the CVE-2019-20894 advisory and the Traefik project's documentation.
References
Related vulnerabilities
Recent vulnerabilities recorded for github.com/traefik/traefik/v2.
