GHSA-f2rj-m42r-6jm2
CRITICALSkipper vulnerable to SSRF via X-Skipper-Proxy
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.
Blast Radius
github.com/zalando/skipperReal-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
Impact
Skipper prior to version v0.13.236 is vulnerable to server-side request forgery (SSRF). An attacker can exploit a vulnerable version of proxy to access the internal metadata server or other unauthenticated URLs by adding an specific header (X-Skipper-Proxy) to the http request.
Patches
The problem was patched in version https://github.com/zalando/skipper/releases/tag/v0.13.237.
Users need to upgrade to skipper >=v0.13.237.
Workarounds
Use dropRequestHeader("X-Skipper-Proxy") filter
References
https://github.com/zalando/skipper/releases/tag/v0.13.237
For more information
If you have any questions or comments about this advisory:
- Open an issue in https://github.com/zalando/skipper/issues/new/choose
- Chat with us in slack: https://app.slack.com/client/T029RQSE6/C82Q5JNH5
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/zalando/skipper | all versions | 0.13.237 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
X-Skipper-Proxy v0.13.237 - Server Side Request Forgery (SSRF)
by Hosein Vita · Mar 28, 2023
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/zalando/skipper. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/zalando/skipper to 0.13.237 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f2rj-m42r-6jm2 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 pinpoints whether GHSA-f2rj-m42r-6jm2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-f2rj-m42r-6jm2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-f2rj-m42r-6jm2 in your dependencies?
O3 detects GHSA-f2rj-m42r-6jm2 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.