# CVE-2021-3998: Information disclosure in glibc

> A flaw in glibc's realpath function may leak sensitive data, requiring OS and library updates to prevent information disclosure.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2022
- **Updated:** 14 Oct 2026
- **Also known as:** AZL-10675, DEBIAN-CVE-2021-3998, GHSA-32pr-wg5j-9rwr, MINI-7whw-ch8g-2hh3

## What is CVE-2021-3998?

CVE-2021-3998 is a high-severity vulnerability in Gnu Glibc, published on 24 Aug 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in glibc. The realpath() function can mistakenly return an unexpected value, potentially leading to information leakage and disclosure of sensitive data.

Weakness: CWE-252 (Unchecked Return Value), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-3998?

It affects 7 products.


Products: Gnu Glibc, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Netapp Ontap Select Deploy Administration Utility.

## How do I fix CVE-2021-3998?

Apply the vendor's patch.

## Is CVE-2021-3998 being exploited?

There is no known exploitation of CVE-2021-3998 in the wild and no public exploit code.

## Other vulnerabilities in Gnu Glibc

- [CVE-2026-5450](https://insights.sbomify.com/CVE-2026-5450/): scanf %mc off-by-one heap buffer overflow (critical 9.8)
- [CVE-2023-25139](https://insights.sbomify.com/CVE-2023-25139/): Memory corruption in n/a (critical 9.8)
- [CVE-1999-0199](https://insights.sbomify.com/CVE-1999-0199/): Other in n/a (critical 9.8)
- [CVE-2019-1010022](https://insights.sbomify.com/CVE-2019-1010022/): Security feature bypass in glibc (critical 9.8)
- [CVE-2005-3590](https://insights.sbomify.com/CVE-2005-3590/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3998 and fix it if it is affected.

What it is: CVE-2021-3998 is a high-severity vulnerability in Gnu Glibc, published on 24 Aug 2022. 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-2021-3998 in the wild and no public exploit code.

Affected product: Gnu Glibc. 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-2021-3998/ (Markdown: https://insights.sbomify.com/CVE-2021-3998/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3998
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3998
- OSV: https://osv.dev/vulnerability/CVE-2021-3998

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3998/
Summaries are generated and may contain mistakes; the official description above is the record.