# CVE-2017-18017: Use after free in n/a

> Remote attackers can trigger a use-after-free in the Linux kernel TCPMSS module, causing denial of service or potential code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Jan 2018
- **Updated:** 3 Jan 2025
- **Also known as:** DEBIAN-CVE-2017-18017, GHSA-3fj5-q6p4-25m2, UBUNTU-CVE-2017-18017

## What is CVE-2017-18017?

CVE-2017-18017 is a critical use after free vulnerability in Canonical Ubuntu Linux, published on 3 Jan 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The tcpmss_mangle_packet function in net/netfilter/xt_TCPMSS.c in the Linux kernel before 4.11, and 4.9.x before 4.9.36, allows remote attackers to cause a denial of service (use-after-free and memory corruption) or possibly have unspecified other impact by leveraging the presence of xt_TCPMSS in an iptables action.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2017-18017?

It affects 29 products.


Products: Arista Eos, Canonical Ubuntu Linux, Debian Debian Linux, F5 Arx, Linux kernel, Openstack Cloud Magnum Orchestration, Opensuse Leap, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Eus, Redhat Enterprise Linux for Real Time, Redhat Enterprise Linux for Real Time for Nfv, Redhat Enterprise Linux Server, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server Tus, Redhat Enterprise Linux Workstation, Redhat Mrg Realtime, Suse Caas Platform, Suse Linux Enterprise Debuginfo, Suse Linux Enterprise Desktop, Suse Linux Enterprise High Availability and 9 more.

## How do I fix CVE-2017-18017?

Apply the vendor's patch.

## Is CVE-2017-18017 being exploited?

There is no known exploitation of CVE-2017-18017 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2026-7473](https://insights.sbomify.com/CVE-2026-7473/): Arista Extensible Operating System Incomplete Comparison with Missing Factors (medium 6.9, exploited in the wild)
- [CVE-2015-8236](https://insights.sbomify.com/CVE-2015-8236/): Privilege escalation in n/a (critical 10.0)
- [CVE-2020-10188](https://insights.sbomify.com/CVE-2020-10188/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-14491](https://insights.sbomify.com/CVE-2017-14491/): Memory corruption in n/a (critical 9.8)
- [CVE-2023-24509](https://insights.sbomify.com/CVE-2023-24509/): Privilege escalation in Arista EOS (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-18017 and fix it if it is affected.

What it is: CVE-2017-18017 is a critical use after free vulnerability in Canonical Ubuntu Linux, published on 3 Jan 2018. 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-2017-18017 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 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-2017-18017/ (Markdown: https://insights.sbomify.com/CVE-2017-18017/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-18017
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-18017
- OSV: https://osv.dev/vulnerability/CVE-2017-18017

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-18017/
Summaries are generated and may contain mistakes; the official description above is the record.