# CVE-2021-45261: Null dereference in n/a

> An attacker can cause a denial of service in GNU patch via an invalid pointer in the another_hunk function.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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:** Yes
- **Published:** 22 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** CLSA-2026-1788355583, DEBIAN-CVE-2021-45261, ECHO-36a0-a7e1-89d6, GHSA-5wqw-cqhv-q8cv, ROOT-OS-DEBIAN-12-CVE-2021-45261, SUSE-SU-2026:0781-1, SUSE-SU-2026:20343-1, SUSE-SU-2026:20431-1, UBUNTU-CVE-2021-45261, openSUSE-SU-2026:10140-1, openSUSE-SU-2026:20227-1

## What is CVE-2021-45261?

CVE-2021-45261 is a medium-severity vulnerability in n/a, published on 22 Dec 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

An Invalid Pointer vulnerability exists in GNU patch 2.7 via the another_hunk function, which causes a Denial of Service.

Weakness: CWE-763 (Release of Invalid Pointer or Reference)

## Which versions are affected by CVE-2021-45261?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `patch` | SUSE:Linux Enterprise Module for Basesystem 15 SP7 | All versions | 2.7.6-150000.5.9.1 |
| `patch` | SUSE:Linux Enterprise Server 16.0 | All versions | 2.7.6-160000.3.1 |
| `patch` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 2.7.6-160000.3.1 |
| `patch` | SUSE:Linux Micro 6.2 | All versions | 2.7.6-160000.3.1 |
| `patch` | openSUSE:Leap 15.6 | All versions | 2.7.6-150000.5.9.1 |
| `patch` | openSUSE:Leap 16.0 | All versions | 2.7.6-160000.3.1 |
| `patch` | openSUSE:Tumbleweed | All versions | 2.8-2.1 |

Products: Gnu Patch.

## How do I fix CVE-2021-45261?

Apply the vendor's patch.

## Is CVE-2021-45261 being exploited?

There is no known exploitation of CVE-2021-45261 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-20969](https://insights.sbomify.com/CVE-2018-20969/): Command injection in n/a (high 7.8)
- [CVE-2018-6952](https://insights.sbomify.com/CVE-2018-6952/): Use after free in n/a (high 7.5)
- [CVE-2019-13636](https://insights.sbomify.com/CVE-2019-13636/): Path traversal in n/a (medium 5.9)
- [CVE-2019-20633](https://insights.sbomify.com/CVE-2019-20633/): Use after free in n/a (medium 5.5)
- [CVE-2016-10713](https://insights.sbomify.com/CVE-2016-10713/): Memory corruption in n/a (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-45261 and fix it if it is affected.

What it is: CVE-2021-45261 is a medium-severity vulnerability in n/a, published on 22 Dec 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-2021-45261 in the wild and no public exploit code.

Affected product: n/a. 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-2021-45261/ (Markdown: https://insights.sbomify.com/CVE-2021-45261/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-45261
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-45261
- OSV: https://osv.dev/vulnerability/CVE-2021-45261

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-45261/
Summaries are generated and may contain mistakes; the official description above is the record.