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Fencer Vulns
medium 6.4

CVE-2020-27837 json

A flaw was found in GDM in versions prior to 3.38.2.1.

published 2020-12-28 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-20336

cvss
6.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

Summary

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.

Patch / fix

  • gnome gnome_display_manager 3.38.2.1
  • gdm3 Debian 14, Debian 13, Debian 12 3.38.2.1-1

debian advisories DEBIAN-CVE-2020-27837

  • gdm openSUSE Tumbleweed 41.0-1.1

opensuse advisories openSUSE-SU-2024:11547-1

  • gdm Arch Linux 3.38.2.1-1

arch linux advisories AVG-1380

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-27837 updated cvss 6.3

gdm: lock screen bypass when autologin is set

  • Red Hat Enterprise Linux 6 gdm, gdm-libs, gdm-plugin-smartcard, gdm-plugin-fingerprint, gdm-user-switch-applet Red Hat Enterprise Linux 7 gdm
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 gdm
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.4 CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.4 AV:L/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • n/a gdm

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.