# CVE-2021-28235: Etcd-io Improper Authentication vulnerability

> Remote attackers can escalate privileges in etcd via the debug function, requiring administrators to upgrade to a patched version.

- **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:** 4 Apr 2023
- **Updated:** 9 Jul 2026
- **Also known as:** AZL-26139, BIT-etcd-2021-28235, DEBIAN-CVE-2021-28235, GHSA-gmph-wf7j-9gcm, UBUNTU-CVE-2021-28235, USN-6189-1, openSUSE-SU-2024:12896-1, openSUSE-SU-2024:13369-1, openSUSE-SU-2024:13370-1, openSUSE-SU-2024:13371-1

## What is CVE-2021-28235?

CVE-2021-28235 is a critical vulnerability in n/a, published on 4 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Authentication vulnerability found in Etcd-io v.3.4.10 allows remote attackers to escalate privileges via the debug function.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-28235?

3 open source packages ship an affected version, including go.etcd.io/etcd/v3 and etcd. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `go.etcd.io/etcd/v3` | Go | All versions | None |
| `go.etcd.io/etcd/v3` | Go | All versions | None |
| `etcd` | Bitnami | From 3.4.10 | 3.4.11 |
| `etcd` | openSUSE:Tumbleweed | All versions | 3.5.8-1.1 |
| `etcd-for-k8s1.25` | openSUSE:Tumbleweed | All versions | 3.5.9-1.1 |
| `etcd-for-k8s1.26` | openSUSE:Tumbleweed | All versions | 3.5.9-1.1 |
| `etcd-for-k8s1.27` | openSUSE:Tumbleweed | All versions | 3.5.9-1.1 |

Products: Etcd Etcd.

## How do I fix CVE-2021-28235?

Upgrade to a fixed version.

## Is CVE-2021-28235 being exploited?

There is no known exploitation of CVE-2021-28235 in the wild and no public exploit code.

Public exploit code:

- CVE-2021-28235 PoC (github_poc): https://github.com/h3ck13r/CVE-2021-28235

## Other vulnerabilities in n/a

- [CVE-2026-33413](https://insights.sbomify.com/CVE-2026-33413/): etcd: Authorization bypasses in multiple APIs (high 8.8)
- [CVE-2022-34038](https://insights.sbomify.com/CVE-2022-34038/): Denial of service in n/a (high 7.5)
- [CVE-2018-16886](https://insights.sbomify.com/CVE-2018-16886/): go.etcd.io/etcd Authentication Bypass (medium 6.8)
- [CVE-2026-59818](https://insights.sbomify.com/CVE-2026-59818/): etcd: gRPC client listener does not enforce `--client-crl-file` certificate revocation (medium 6.5)
- [CVE-2020-15106](https://insights.sbomify.com/CVE-2020-15106/): Improper Input Validation in etcd (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28235 and fix it if it is affected.

What it is: CVE-2021-28235 is a critical vulnerability in n/a, published on 4 Apr 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-2021-28235 in the wild and no public exploit code.

Affected packages and fixed versions:
- go.etcd.io/etcd/v3 (Go): affected all versions; no fix listed
- go.etcd.io/etcd/v3 (Go): affected all versions; no fix listed
- etcd (Bitnami): affected from 3.4.10; fixed in 3.4.11

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-2021-28235/ (Markdown: https://insights.sbomify.com/CVE-2021-28235/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28235
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28235
- OSV: https://osv.dev/vulnerability/CVE-2021-28235

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28235/
Summaries are generated and may contain mistakes; the official description above is the record.