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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-8833
• https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1862933
• https://usn.ubuntu.com/4315-1/
• https://usn.ubuntu.com/4315-2/