# GHSA-h8g9-6gvh-5mrc: etcd vulnerable to TOCTOU of gateway endpoint authentication

> An attacker can bypass authentication in etcd gateway if endpoint settings change after initial DNS-based validation, requiring specific gateway configuration.

- **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:** 6 Oct 2022

## What is GHSA-h8g9-6gvh-5mrc?

GHSA-h8g9-6gvh-5mrc is an authentication bypass vulnerability in go.etcd.io/etcd/v3, published on 6 Oct 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Vulnerability type
Authentication

### Workarounds
Refer to the [gateway documentation](https://github.com/etcd-io/etcd/blob/master/Documentation/op-guide/gateway.md). The vulnerability was spotted due to unclear documentation of how the gateway handles endpoints validation. 

### Detail
The gateway only authenticates endpoints detected from DNS SRV records, and it only authenticates the detected endpoints once. Therefore, if an endpoint changes its authentication settings, the gateway will continue to assume the endpoint is still authenticated. The auditors has noted that appropriate documentation of this validation functionality plus deprecation of this misleading functionality is an acceptable path forward.

### References
Find out more on this vulnerability in the [security audit report](https://github.com/etcd-io/etcd/blob/master/security/SECURITY_AUDIT.pdf)

### For more information
If you have any questions or comments about this advisory:
* Contact the [etcd security committee](https://github.com/etcd-io/etcd/blob/master/security/security-release-process.md#product-security-committee-psc)

## Which versions are affected by GHSA-h8g9-6gvh-5mrc?

4 open source packages ship an affected version, including go.etcd.io/etcd/v3.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `go.etcd.io/etcd/v3` | Go | All versions | 3.3.23 |
| `go.etcd.io/etcd/v3` | Go | All versions | 3.3.23 |
| `go.etcd.io/etcd/v3` | Go | From 3.4.0 | 3.4.10 |
| `go.etcd.io/etcd/v3` | Go | From 3.4.0 | 3.4.10 |

## How do I fix GHSA-h8g9-6gvh-5mrc?

Upgrade go.etcd.io/etcd/v3 to a fixed version for your release line: 3.3.23 or 3.4.10.

## Is GHSA-h8g9-6gvh-5mrc being exploited?

There is no known exploitation of GHSA-h8g9-6gvh-5mrc in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-h8g9-6gvh-5mrc and fix it if it is affected.

What it is: GHSA-h8g9-6gvh-5mrc is an authentication bypass vulnerability in go.etcd.io/etcd/v3, published on 6 Oct 2022. 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-h8g9-6gvh-5mrc in the wild and no public exploit code.

Affected packages and fixed versions:
- go.etcd.io/etcd/v3 (Go): affected all versions; fixed in 3.3.23
- go.etcd.io/etcd/v3 (Go): affected all versions; fixed in 3.3.23
- go.etcd.io/etcd/v3 (Go): affected from 3.4.0; fixed in 3.4.10
- go.etcd.io/etcd/v3 (Go): affected from 3.4.0; fixed in 3.4.10

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-h8g9-6gvh-5mrc/ (Markdown: https://insights.sbomify.com/GHSA-h8g9-6gvh-5mrc/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-h8g9-6gvh-5mrc

---
From sbomify Insights: https://insights.sbomify.com/GHSA-h8g9-6gvh-5mrc/
Summaries are generated and may contain mistakes; the official description above is the record.