# CVE-2020-8833: Apport race condition in crash report permissions

> A race condition in Apport allows local attackers to escalate privileges to root if symlink protection is disabled.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N`)
- **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:** 22 Apr 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-w9g5-3qgc-xmgx, UBUNTU-CVE-2020-8833

## What is CVE-2020-8833?

CVE-2020-8833 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 22 Apr 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Time-of-check Time-of-use Race Condition vulnerability on crash report ownership change in Apport allows for a possible privilege escalation opportunity. If fs.protected_symlinks is disabled, this can be exploited between the os.open and os.chown calls when the Apport cron script clears out crash files of size 0. A symlink with the same name as the deleted file can then be created upon which chown will be called, changing the file owner to root. Fixed in versions 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8 and 2.20.11-0ubuntu22.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2020-8833?

It affects 2 products.


Products: Apport Project Apport, Canonical Ubuntu Linux.

## How do I fix CVE-2020-8833?

Apply the vendor's patch.

## Is CVE-2020-8833 being exploited?

There is no known exploitation of CVE-2020-8833 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2022-28657](https://insights.sbomify.com/CVE-2022-28657/): Denial of service in Apport (high 7.8)
- [CVE-2018-6552](https://insights.sbomify.com/CVE-2018-6552/): Apport treats the container PID as the global PID when /proc/<global_pid>/ is missing (high 7.8)
- [CVE-2017-14177](https://insights.sbomify.com/CVE-2017-14177/): Privilege escalation in Apport (high 7.8)
- [CVE-2017-14179](https://insights.sbomify.com/CVE-2017-14179/): Privilege escalation in Apport (high 7.8)
- [CVE-2017-14180](https://insights.sbomify.com/CVE-2017-14180/): Privilege escalation in Apport (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-8833 and fix it if it is affected.

What it is: CVE-2020-8833 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 22 Apr 2020. 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-2020-8833 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-2020-8833/ (Markdown: https://insights.sbomify.com/CVE-2020-8833/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-8833
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-8833
- OSV: https://osv.dev/vulnerability/CVE-2020-8833

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-8833/
Summaries are generated and may contain mistakes; the official description above is the record.