CVE-2023-47106 — v2
MEDIUMCVE-2023-47106 is a medium-severity (CVSS 4.8) Improper Input Validation vulnerability in github.com/traefik/traefik/v2. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/traefik/traefik/v2 — see the affected versions and patch details below.
Incorrect processing of fragment in the URL leads to Authorization Bypass in Traefik
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-47106 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/traefik/traefik/v2🐹github.com/traefik/traefik/v3Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/traefik/traefik/v2 | all versions | 2.10.6go get github.com/traefik/traefik/v2@v2.10.6 |
| 🐹Go | github.com/traefik/traefik/v3 | all versions | 3.0.0-beta5go get github.com/traefik/traefik/v3@v3.0.0-beta5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/traefik/traefik/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/traefik/traefik/v2 to 2.10.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-47106 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-47106 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-47106. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-47106 in your dependencies?
O3 Security finds CVE-2023-47106 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.