# GHSA-c66w-hq56-4q97: Network policy may be bypassed by some ICMP Echo Requests

> Attackers can bypass network policies via ICMP Echo Requests under specific conditions, allowing unauthorized access to protected endpoints.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 May 2021
- **Also known as:** GO-2022-0393

## What is GHSA-c66w-hq56-4q97?

GHSA-c66w-hq56-4q97 is a vulnerability in github.com/cilium/cilium, published on 21 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

## Impact

Under certain conditions, ICMP Echo Request sent to a Cilium endpoint from an actor may bypass a network policy which _disallows_ access from the actor to the endpoint, but _allows_ from the endpoint to the actor. This does _NOT_ apply to UDP and TCP traffic.

The actor is either a pod or a cluster host or a remote host.

The following conditions must be met:
1. Network policies have been created which:
  a) do not allow access from the actor to the endpoint;
  b) allow access from the endpoint to the actor and does not specify neither protocol nor port. 
2. The endpoint has sent ICMP Echo Request to the actor with the ICMP identifier X.
3. The actor sends ICMP Echo Request to the endpoint with the same ICMP identifier X.
4. The request from the actor (3.) is sent before the Cilium's conntrack GC has removed the previously created conntrack entry (2.).

## Detailed description

See https://github.com/cilium/cilium/commit/dfb008a9099c4da1e0fd964c899c43ee13280b0e (v1.9.x), https://github.com/cilium/cilium/commit/ff6ebae6efca1bd991302b464dea428512823e79 (v1.8.x), https://github.com/cilium/cilium/commit/472bbeff75161979c317ab21d563f826291b5f37 (v1.7.x).

## Example

```
$ kubectl run server --image=quay.io/cilium/net-test:v1.0.0 --restart=Never -- sleep 3600
$ kubectl run client --image=quay.io/cilium/net-test:v1.0.0 --restart=Never -- sleep 3600
$ cat <<EOF | kubectl apply -f
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: server-netpol # allow client->server
spec:
  podSelector:
    matchLabels:
      run: server
  ingress:
  - from:
    - podSelector:
        matchLabels:
          run: client
  policyTypes:
  - Ingress
---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: client-netpol # deny any->client
spec:
  podSelector:
    matchLabels:
      run: client
  policyTypes:
  - Ingress
EOF

$ kubectl exec -ti server -- xping -c1 -x666 $CLIENT_POD_IP
PING 10.154.0.50 (10.154.0.50): 56 data bytes
^C
--- 10.154.0.50 ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss   <--- "client-netpol" policy denied
command terminated with exit code 1

$ kubectl exec -ti client -- xping -c1 -x666 $SERVER_POD_IP
PING 10.154.1.16 (10.154.1.16): 56 data bytes
64 bytes from 10.154.1.16: seq=0 ttl=60 time=0.822 ms

--- 10.154.1.16 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss   <--- "server-netpol" policy allowed
round-trip min/avg/max = 0.822/0.822/0.822 ms

$ kubectl exec -ti server -- xping -c1 -x666 $CLIENT_POD_IP
PING 10.154.0.50 (10.154.0.50): 56 data bytes
64 bytes from 10.154.0.50: seq=0 ttl=60 time=0.527 ms

--- 10.154.0.50 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss   <--- "client-netpol" policy bypassed
round-trip min/avg/max = 0.527/0.527/0.527 ms
```

## For more information

If you have any questions or comments about this advisory:

- Open an issue in [Cilium Issues](https://github.com/cilium/cilium/issues)
- Email us at security@cilium.io

## Which versions are affected by GHSA-c66w-hq56-4q97?

7 open source packages ship an affected version, including github.com/cilium/cilium.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/cilium/cilium` | Go | From 1.7.8 | 1.7.15, 1.8.8, 1.9.5 |
| `github.com/cilium/cilium` | Go | From 1.7.8 | 1.7.15 |
| `github.com/cilium/cilium` | Go | From 1.7.8 | 1.7.15 |
| `github.com/cilium/cilium` | Go | From 1.8.3 | 1.8.8 |
| `github.com/cilium/cilium` | Go | From 1.8.3 | 1.8.8 |
| `github.com/cilium/cilium` | Go | From 1.9.0 | 1.9.5 |
| `github.com/cilium/cilium` | Go | From 1.9.0 | 1.9.5 |

## How do I fix GHSA-c66w-hq56-4q97?

Upgrade github.com/cilium/cilium to a fixed version for your release line: 1.7.15, 1.8.8 or 1.9.5.

## Is GHSA-c66w-hq56-4q97 being exploited?

There is no known exploitation of GHSA-c66w-hq56-4q97 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-c66w-hq56-4q97 and fix it if it is affected.

What it is: GHSA-c66w-hq56-4q97 is a vulnerability in github.com/cilium/cilium, published on 21 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-c66w-hq56-4q97 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/cilium/cilium (Go): affected from 1.7.8; fixed in 1.7.15, 1.8.8, 1.9.5
- github.com/cilium/cilium (Go): affected from 1.7.8; fixed in 1.7.15
- github.com/cilium/cilium (Go): affected from 1.7.8; fixed in 1.7.15
- github.com/cilium/cilium (Go): affected from 1.8.3; fixed in 1.8.8
- github.com/cilium/cilium (Go): affected from 1.8.3; fixed in 1.8.8
- github.com/cilium/cilium (Go): affected from 1.9.0; fixed in 1.9.5
- github.com/cilium/cilium (Go): affected from 1.9.0; fixed in 1.9.5

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-c66w-hq56-4q97/ (Markdown: https://insights.sbomify.com/GHSA-c66w-hq56-4q97/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-c66w-hq56-4q97

---
From sbomify Insights: https://insights.sbomify.com/GHSA-c66w-hq56-4q97/
Summaries are generated and may contain mistakes; the official description above is the record.