CVE-2023-47106: Incorrect processing of fragment in the URL leads to Authorization Bypass in Traefik
First published: Mon Dec 04 2023(Updated: )
### Summary When a request is sent to Traefik with a URL fragment, Traefik automatically URL encodes and forwards the fragment to the backend server. This violates the RFC because in the origin-form the URL should only contain the absolute path and the query. When this is combined with another frontend proxy like Nginx, it can be used to bypass frontend proxy URI-based access control restrictions. ### Details For example, we have this Nginx configuration: ``` location /admin { deny all; return 403; } ``` This can be bypassed when the attacker is requesting to /#/../admin This won’t be vulnerable if the backend server follows the RFC and ignores any characters after the fragment. However, if Nginx is chained with another reverse proxy which automatically URL encode the character # (Traefik) the URL will become /%23/../admin And allow the attacker to completely bypass the Access Restriction from the Nginx Front-End proxy. Here is a diagram to summarize the attack:  ### PoC  This is the POC docker I've set up. It contains Nginx, Traefik proxies and a backend server running PHP. https://drive.google.com/file/d/1vLnA0g7N7ZKhLNmHmuJ4JJjV_J2akNMt/view?usp=sharing ### Impact This allows the attacker to completely bypass the Access Restriction from Front-End proxy.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| go/github.com/traefik/traefik/v3 | <3.0.0-beta5 | 3.0.0-beta5 |
| go/github.com/traefik/traefik/v2 | <2.10.6 | 2.10.6 |
| Traefik Traefik | <=2.10.5 | |
| Traefik Traefik | =3.0.0-beta1 | |
| Traefik Traefik | =3.0.0-beta2 | |
| Traefik Traefik | =3.0.0-beta3 | |
| Traefik Traefik | =3.0.0-beta4 |
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Reference Links
- https://github.com/traefik/traefik/security/advisories/GHSA-fvhj-4qfh-q2hm
- https://datatracker.ietf.org/doc/html/rfc7230#section-5.3.1
- https://github.com/traefik/traefik/releases/tag/v2.10.6
- https://github.com/traefik/traefik/releases/tag/v3.0.0-beta5
- https://nvd.nist.gov/vuln/detail/CVE-2023-47106
- https://github.com/advisories/GHSA-fvhj-4qfh-q2hm (Advisory)
Frequently Asked Questions
What is the vulnerability ID for this issue?
The vulnerability ID for this issue is CVE-2023-47106.
What is the title of this vulnerability?
The title of this vulnerability is 'Incorrect processing of fragment in the URL leads to Authorization Bypass in Traefik'.
What is the severity level of CVE-2023-47106?
The severity level of CVE-2023-47106 is medium.
How does CVE-2023-47106 impact Traefik?
CVE-2023-47106 impacts Traefik by allowing for authorization bypass due to incorrect processing of URL fragments.
How can I fix CVE-2023-47106?
To fix CVE-2023-47106, update Traefik to version 2.10.6 or 3.0.0-beta5, depending on your currently used version.
- collector/github-advisory-latest
- alias/GHSA-fvhj-4qfh-q2hm
- alias/CVE-2023-47106
- collector/github-advisory
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- version/traefik traefik/3.0.0-beta1
- version/traefik traefik/3.0.0-beta2
- version/traefik traefik/3.0.0-beta3
- version/traefik traefik/3.0.0-beta4