# CVE-2018-15686: systemd: reexec state injection: fgets() on overlong lines leads to line splitting

> An attacker can inject arbitrary state during systemd re-execution via NotifyAccess, potentially leading to root privilege escalation or code execution.

- **Severity:** High 7.0 (`CVSS:3.0/AV:L/AC:H/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:** 26 Oct 2018
- **Updated:** 9 Jun 2025
- **Also known as:** DEBIAN-CVE-2018-15686, GHSA-86rx-vp92-xvgg, UBUNTU-CVE-2018-15686

## What is CVE-2018-15686?

CVE-2018-15686 is a high-severity unsafe deserialization vulnerability in Canonical Ubuntu Linux, published on 26 Oct 2018. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in unit_deserialize of systemd allows an attacker to supply arbitrary state across systemd re-execution via NotifyAccess. This can be used to improperly influence systemd execution and possibly lead to root privilege escalation. Affected releases are systemd versions up to and including 239.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2018-15686?

It affects 4 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Oracle Communications Cloud Native Core Network Function Cloud Native Environment, Systemd Project Systemd.

## How do I fix CVE-2018-15686?

Apply the vendor's patch.

## Is CVE-2018-15686 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-15686 exists.

Public exploit code:

- systemd - 'reexec' State Injection (exploitdb)
- Remediation task for CVE-2018-15686, CVE-2018-16866, and CVE-2018-16888 affecting SystemD in EL7 (github_poc): https://github.com/hpcprofessional/remediate_cesa_2019_2091

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-15686 and fix it if it is affected.

What it is: CVE-2018-15686 is a high-severity unsafe deserialization vulnerability in Canonical Ubuntu Linux, published on 26 Oct 2018. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-15686 exists.

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-2018-15686/ (Markdown: https://insights.sbomify.com/CVE-2018-15686/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-15686
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-15686
- OSV: https://osv.dev/vulnerability/CVE-2018-15686

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-15686/
Summaries are generated and may contain mistakes; the official description above is the record.