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CVE-2020-8833

Published: 2 April 2020

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.

Mitigation

This ability to exploit this is likely mitigated by the Ubuntu default of
fs.protected_symlinks=1

Priority

Medium

Cvss 3 Severity Score

4.7

Score breakdown

Status

Package Release Status
apport
Launchpad, Ubuntu, Debian
bionic
Released (2.20.9-0ubuntu7.14)
eoan
Released (2.20.11-0ubuntu8.8)
focal
Released (2.20.11-0ubuntu22)
trusty
Released (2.14.1-0ubuntu3.29+esm4)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only)
upstream Needs triage

xenial
Released (2.20.1-0ubuntu2.23)

Severity score breakdown

Parameter Value
Base score 4.7
Attack vector Local
Attack complexity High
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact None
Availability impact None
Vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N