CVE-2020-27837

Publication date 28 December 2020

Last updated 26 August 2025

Ubuntu priority

Low

Why this priority?

Cvss 3 Severity Score

6.4 · Medium

Score breakdown

Description

A flaw was found in GDM in versions prior to 3.38.2.1. A race condition in the handling of session shutdown makes it possible to bypass the lock screen for a user that has autologin enabled, accessing their session without authentication. This is similar to CVE-2017-12164, but requires more difficult conditions to exploit.

Read the notes from the security team

Status

Package Ubuntu Release Status
gdm3 25.10 questing
Not affected
25.04 plucky
Not affected
24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic Ignored end of life, was needed
22.04 LTS jammy
Vulnerable
21.10 impish Ignored end of life
21.04 hirsute Ignored end of life
20.10 groovy Ignored end of life
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release

Notes

mdeslaur

unlikely scenario, requires autologin to be enabled and for a session to crash but then still work. Setting priority to "low"

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
gdm3

Severity score breakdown

Parameter Value
Base score 6.4 · Medium
Attack vector Physical
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Other references