CVE-2020-28049: An issue was discovered in SDDM before 0.19.0

Q: How do I fix CVE-2020-28049?

sddm: upgrade to 0.19.0; leap: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2020-28049 being exploited?

CVE-2020-28049 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-28049 affect?

CVE-2020-28049 affects sddm, leap, debian linux. Severity is medium (CVSS 6.3). An issue was discovered in SDDM before 0.19.0. It incorrectly starts the X server in a way that - for a short time period - allows local unprivileged users to create a connection to the X server without providing proper authentication. A lo

Q: How urgent is CVE-2020-28049?

Priority 41/100. Public exploit reference; On your watchlist

This month

MEDIUM 6.3WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2020-28049 is a medium-severity flaw (CVSS 6.3) affecting sddm, leap, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in SDDM before 0.19.0. It incorrectly starts the X server in a way that - for a short time period - allows local unprivileged users to create a connection to the X server without providing proper authentication. A local attacker can thus access X server display contents and, for example, intercept keystrokes or access the clipboard. This is caused by a race condition during Xauthority file creation.

Why this priority

Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.3 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-362
Published	2020-11-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · fedoraproject · opensuse · sddm project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-11-04 19:15 UTCPublished CVE record published
2026-06-17 03:10 UTCUpdated Record last modified

sddm project sddm UPGRADE

Affected: < 0.19.0

Fixed in: 0.19.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sddm || rpm -q sddm || sddm --version

2. UPGRADE to 0.19.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sddm

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sddm

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

opensuse leap MITIGATE

Affected: 15.1 · 15.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 15.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 33

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-28049?

sddm: upgrade to 0.19.0; leap: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-28049 being exploited?

CVE-2020-28049 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-28049 affect?

CVE-2020-28049 affects sddm, leap, debian linux. Severity is medium (CVSS 6.3). An issue was discovered in SDDM before 0.19.0. It incorrectly starts the X server in a way that - for a short time period - allows local unprivileged users to create a connection to the X server without providing proper authentication. A lo

How urgent is CVE-2020-28049?

Priority 41/100. Public exploit reference; On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

CVE-2018-14345 HIGH 7.5 UPGRADE An issue was discovered in SDDM through 0.17.0

References

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