# CVE-2023-48312: Authentication bypass using an empty token in capsule-proxy

> Attackers can bypass authentication in capsule-proxy when anonymous-auth is disabled, leading to privilege escalation against the Kubernetes API.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Nov 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-fpvw-6m5v-hqfp, GO-2023-2351

## What is CVE-2023-48312?

CVE-2023-48312 is a critical authentication bypass vulnerability in projectcapsule capsule-proxy, published on 24 Nov 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

capsule-proxy is a reverse proxy for the capsule operator project. Affected versions are subject to a privilege escalation vulnerability which is based on a missing check if the user is authenticated based on the `TokenReview` result. All the clusters running with the `anonymous-auth` Kubernetes API Server setting disable (set to `false`) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server. This privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS). This vulnerability has been addressed in version 0.4.6. Users are advised to upgrade.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2023-48312?

5 open source packages ship an affected version, including github.com/projectcapsule/capsule-proxy and github.com/clastix/capsule-proxy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/projectcapsule/capsule-proxy` | Go | All versions | 0.4.6 |
| `github.com/projectcapsule/capsule-proxy` | Go | All versions | 0.4.6 |
| `github.com/projectcapsule/capsule-proxy` | Go | All versions | 0.4.6 |
| `github.com/clastix/capsule-proxy` | Go | All versions | 0.4.6 |
| `github.com/clastix/capsule-proxy` | Go | All versions | 0.4.6 |

Products: Clastix Capsule-Proxy.

## How do I fix CVE-2023-48312?

Upgrade github.com/projectcapsule/capsule-proxy to 0.4.6 or later.

## Is CVE-2023-48312 being exploited?

There is no known exploitation of CVE-2023-48312 in the wild and no public exploit code.

## Other vulnerabilities in projectcapsule capsule-proxy

- [CVE-2022-23652](https://insights.sbomify.com/CVE-2022-23652/): Privilege escalation using hop-by-hop Connection header (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-48312 and fix it if it is affected.

What it is: CVE-2023-48312 is a critical authentication bypass vulnerability in projectcapsule capsule-proxy, published on 24 Nov 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-48312 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/projectcapsule/capsule-proxy (Go): affected all versions; fixed in 0.4.6
- github.com/projectcapsule/capsule-proxy (Go): affected all versions; fixed in 0.4.6
- github.com/projectcapsule/capsule-proxy (Go): affected all versions; fixed in 0.4.6
- github.com/clastix/capsule-proxy (Go): affected all versions; fixed in 0.4.6
- github.com/clastix/capsule-proxy (Go): affected all versions; fixed in 0.4.6

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/CVE-2023-48312/ (Markdown: https://insights.sbomify.com/CVE-2023-48312/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-48312
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-48312
- OSV: https://osv.dev/vulnerability/CVE-2023-48312

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-48312/
Summaries are generated and may contain mistakes; the official description above is the record.