# CVE-2021-3999: Memory corruption in glibc

> A local attacker can exploit an off-by-one error in glibc's getcwd function to execute arbitrary code and escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2022
- **Updated:** 14 Oct 2026
- **Also known as:** CLSA-2022-1648138064, CLSA-2022-1648138117, CLSA-2022-1648147764, CLSA-2022-1648149189, CLSA-2022-1648149396, DEBIAN-CVE-2021-3999, GHSA-vfch-2fr8-r5c2, MGASA-2022-0052, UBUNTU-CVE-2021-3999

## What is CVE-2021-3999?

CVE-2021-3999 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 24 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in glibc. An off-by-one buffer overflow and underflow in getcwd() may lead to memory corruption when the size of the buffer is exactly 1. A local attacker who can control the input buffer and size passed to getcwd() in a setuid program could use this flaw to potentially execute arbitrary code and escalate their privileges on the system.

Weakness: CWE-193 (Off-by-one Error)

## Which versions are affected by CVE-2021-3999?

It affects 10 products.


Products: Debian Debian Linux, Gnu Glibc, Netapp E-Series Performance Analyzer, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Netapp Nfs Plug-In, Netapp Ontap Select Deploy Administration Utility.

## How do I fix CVE-2021-3999?

Apply the vendor's patch.

## Is CVE-2021-3999 being exploited?

There is no known exploitation of CVE-2021-3999 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3999 and fix it if it is affected.

What it is: CVE-2021-3999 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 24 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3999 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-3999/ (Markdown: https://insights.sbomify.com/CVE-2021-3999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3999
- OSV: https://osv.dev/vulnerability/CVE-2021-3999

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3999/
Summaries are generated and may contain mistakes; the official description above is the record.