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CVE-2020-8833

Publication date 2 April 2020

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

4.7 · Medium

Score breakdown

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

Status

Package Ubuntu Release Status
apport 20.04 LTS focal
Fixed 2.20.11-0ubuntu22
19.10 eoan
Fixed 2.20.11-0ubuntu8.8
18.04 LTS bionic
Fixed 2.20.9-0ubuntu7.14
16.04 LTS xenial
Fixed 2.20.1-0ubuntu2.23
14.04 LTS trusty

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Severity score breakdown

Parameter Value
Base score 4.7 · Medium
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

References

Related Ubuntu Security Notices (USN)

Other references