# CVE-2019-15239: Use after free in n/a

> A local attacker can trigger use-after-free conditions in the Linux kernel TCP output handling, leading to privilege escalation or system crashes.

- **Severity:** High 7.8 (`CVSS:3.0/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:** 20 Aug 2019
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-15239, GHSA-7j8w-38v5-7qqp, UBUNTU-CVE-2019-15239

## What is CVE-2019-15239?

CVE-2019-15239 is a high-severity use after free vulnerability in Debian Debian Linux, published on 20 Aug 2019. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, a certain net/ipv4/tcp_output.c change, which was properly incorporated into 4.16.12, was incorrectly backported to the earlier longterm kernels, introducing a new vulnerability that was potentially more severe than the issue that was intended to be fixed by backporting. Specifically, by adding to a write queue between disconnection and re-connection, a local attacker can trigger multiple use-after-free conditions. This can result in a kernel crash, or potentially in privilege escalation. NOTE: this affects (for example) Linux distributions that use 4.9.x longterm kernels before 4.9.190 or 4.14.x longterm kernels before 4.14.139.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2019-15239?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2019-15239?

Apply the vendor's patch.

## Is CVE-2019-15239 being exploited?

There is no known exploitation of CVE-2019-15239 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-2019-15239 and fix it if it is affected.

What it is: CVE-2019-15239 is a high-severity use after free vulnerability in Debian Debian Linux, published on 20 Aug 2019. 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-2019-15239 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-2019-15239/ (Markdown: https://insights.sbomify.com/CVE-2019-15239/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-15239
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-15239
- OSV: https://osv.dev/vulnerability/CVE-2019-15239

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-15239/
Summaries are generated and may contain mistakes; the official description above is the record.