# Access Restriction Bypass in kube-apiserver

Advisory record · `GHSA-g42g-737j-qx6j`

- **Identifiers:** `GHSA-g42g-737j-qx6j` · `CVE-2021-25735` · `GO-2022-0907`
- **State:** Confirmed
- **Severity:** CVSS 6.5 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-284](https://cwe.mitre.org/data/definitions/284.html) · [CWE-372](https://cwe.mitre.org/data/definitions/372.html) · [CWE-863](https://cwe.mitre.org/data/definitions/863.html)
- **Tags:** [Broken access control](https://agentprime.io/advisories/tag/access-control.md) · [CWE-372](https://agentprime.io/advisories/tag/cwe-372.md)
- **Published:** 28 May 2021
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 28 May 2021, 19:49 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `k8s.io/kubernetes` (Go): affected `>=1.20.0, <1.20.6 || >=1.19.0, <1.19.10 || <1.18.18`; fixed in `1.20.6`, `1.19.10`, `1.18.18`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.5 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H`, from CNA (kubernetes)

- **CISA KEV:** Not listed.
- **EPSS:** 0.054, the 92nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:44 UTC: First seen by agentprime
- 31 Oct 2026, 14:44 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-g42g-737j-qx6j)

## Sources

- [GitHub Advisory Database: GHSA-g42g-737j-qx6j](https://github.com/advisories/GHSA-g42g-737j-qx6j)
- [OSV: GHSA-g42g-737j-qx6j](https://osv.dev/vulnerability/GHSA-g42g-737j-qx6j)
- <https://nvd.nist.gov/vuln/detail/CVE-2021-25735>
- <https://github.com/kubernetes/kubernetes/issues/100096>
- <https://github.com/kubernetes/kubernetes/pull/99946>
- <https://github.com/kubernetes/kubernetes/commit/00e81db174ef7aca497be5f42d87e46d14df2a90>
- <https://bugzilla.redhat.com/show_bug.cgi?id=1937562>
- <https://github.com/kubernetes/kubernetes>
- <https://groups.google.com/g/kubernetes-security-announce/c/FKAGqT4jx9Y>
- <https://pkg.go.dev/k8s.io/kubernetes@v1.23.5/cmd/kube-apiserver>
- <https://sysdig.com/blog/cve-2021-25735-kubernetes-admission-bypass>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-g42g-737j-qx6j>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-g42g-737j-qx6j/>. Everything for agents: <https://agentprime.io/llms.txt>.