# CVE-2021-29221: Privilege escalation in Erlang/OTP

> Local attackers can escalate privileges to SYSTEM or hijack accounts via unsafe filesystem permissions on Windows.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-gq7g-854q-935r

## What is CVE-2021-29221?

CVE-2021-29221 is a high-severity vulnerability in Erlang/OTP, published on 9 Apr 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A local privilege escalation vulnerability was discovered in Erlang/OTP prior to version 23.2.3. By adding files to an existing installation's directory, a local attacker could hijack accounts of other users running Erlang programs or possibly coerce a service running with "erlsrv.exe" to execute arbitrary code as Local System. This can occur only under specific conditions on Windows with unsafe filesystem permissions.

Weakness: CWE-426 (Untrusted Search Path)

## Which versions are affected by CVE-2021-29221?

It affects 1 product.


Products: Erlang Erlang\/Otp.

## How do I fix CVE-2021-29221?

No fix has been published for CVE-2021-29221 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-29221 being exploited?

There is no known exploitation of CVE-2021-29221 in the wild and no public exploit code.

## Other vulnerabilities in Erlang/OTP

- [CVE-2022-37026](https://insights.sbomify.com/CVE-2022-37026/): Auth bypass in n/a (critical 9.8)
- [CVE-2016-10253](https://insights.sbomify.com/CVE-2016-10253/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-55953](https://insights.sbomify.com/CVE-2026-55953/): TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication (critical 9.1)
- [CVE-2026-49759](https://insights.sbomify.com/CVE-2026-49759/): Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash (high 8.8)
- [CVE-2026-58227](https://insights.sbomify.com/CVE-2026-58227/): TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-29221 and fix it if it is affected.

What it is: CVE-2021-29221 is a high-severity vulnerability in Erlang/OTP, published on 9 Apr 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-29221 in the wild and no public exploit code.

Affected product: Erlang/OTP. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2021-29221/ (Markdown: https://insights.sbomify.com/CVE-2021-29221/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29221
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29221
- OSV: https://osv.dev/vulnerability/CVE-2021-29221

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-29221/
Summaries are generated and may contain mistakes; the official description above is the record.