# CVE-2019-20633: Use after free in n/a

> A double-free vulnerability in GNU patch allows attackers to cause a denial of service via a crafted patch file.

- **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:** 25 Mar 2020
- **Updated:** 5 Aug 2024
- **Also known as:** ALPINE-CVE-2019-20633, AZL-35107, AZL-6791, CLEANSTART-2026-KM86582, GHSA-w88p-xvmw-fxgg, JLSEC-2026-18, SUSE-SU-2024:2704-1, SUSE-SU-2024:2780-1, SUSE-SU-2025:20075-1, UBUNTU-CVE-2019-20633, openSUSE-SU-2024:14239-1

## What is CVE-2019-20633?

CVE-2019-20633 is a medium-severity use after free vulnerability in n/a, published on 25 Mar 2020. 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

GNU patch through 2.7.6 contains a free(p_line[p_end]) Double Free vulnerability in the function another_hunk in pch.c that can cause a denial of service via a crafted patch file. NOTE: this issue exists because of an incomplete fix for CVE-2018-6952.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2019-20633?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `patch` | SUSE:Linux Enterprise Module for Basesystem 15 SP5 | All versions | 2.7.6-150000.5.6.1 |
| `patch` | SUSE:Linux Enterprise Module for Basesystem 15 SP6 | All versions | 2.7.6-150000.5.6.1 |
| `patch` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 2.7.5-8.11.1 |
| `patch` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 2.7.5-8.11.1 |
| `patch` | SUSE:Linux Micro 6.0 | All versions | 2.7.6-3.1 |
| `patch` | openSUSE:Leap 15.5 | All versions | 2.7.6-150000.5.6.1 |
| `patch` | openSUSE:Leap 15.6 | All versions | 2.7.6-150000.5.6.1 |
| `patch` | openSUSE:Tumbleweed | All versions | 2.7.6-8.1 |

Products: Gnu Patch.

## How do I fix CVE-2019-20633?

Apply the vendor's patch.

## Is CVE-2019-20633 being exploited?

There is no known exploitation of CVE-2019-20633 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-2021-45261](https://insights.sbomify.com/CVE-2021-45261/): Null dereference 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-2019-20633 and fix it if it is affected.

What it is: CVE-2019-20633 is a medium-severity use after free vulnerability in n/a, published on 25 Mar 2020. 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-2019-20633 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-2019-20633/ (Markdown: https://insights.sbomify.com/CVE-2019-20633/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-20633
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-20633
- OSV: https://osv.dev/vulnerability/CVE-2019-20633

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-20633/
Summaries are generated and may contain mistakes; the official description above is the record.