GHSA-5r23-prx4-mqg3
MEDIUMCilium may not enforce host firewall policies when Native Routing, WireGuard and Node Encryption are enabled
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/cilium/ciliumReal-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
Host Policies will incorrectly permit traffic from Pods on other nodes when all of the following configurations are enabled:
These options are disabled by default in Cilium.
Patches
This issue was fixed by #42892.
This issue affects:
- Cilium v1.18 between v1.18.0 and v1.18.5 inclusive
This issue is fixed in:
- Cilium v1.18.6
Workarounds
There is currently no officially verified or comprehensive workaround for this issue. The following procedure has been validated strictly within a local 'Kind' environment and has not undergone exhaustive testing across diverse production architectures. Proceed with caution.
To mitigate the identified traffic bypass, ensure all ingress traffic from the cilium_wg0 interface is explicitly routed to cilium_host for policy enforcement. This ensures that host-level security policies are applied to decrypted WireGuard traffic. Execute the following configuration on each CiliumNode:
# IPv4 Traffic
ip rule add iif cilium_wg0 table 300
ip route add default dev cilium_host table 300
# IPv6 Traffic
ip -6 rule add iif cilium_wg0 table 300
ip -6 route add default dev cilium_net table 300
Acknowledgements
Special thanks to @julianwiedmann for reporting the issue and helping with the resolution.
For more information
If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated as top priority. Please also address any comments or questions on this advisory to the same mailing list.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cilium/cilium | ≥ 1.18.0&&< 1.18.6 | 1.18.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cilium/cilium. 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/cilium/cilium to 1.18.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5r23-prx4-mqg3 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-5r23-prx4-mqg3 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-5r23-prx4-mqg3. 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-5r23-prx4-mqg3 in your dependencies?
O3 detects GHSA-5r23-prx4-mqg3 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.