#VU48419 Race condition in sddm - CVE-2020-28049

Vulnerability identifier: #VU48419

Vulnerability risk: Low

CVSSv4.0: 4.1 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-28049

CWE-ID: CWE-362

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
sddm
Other software / Other software solutions

Vendor: Simple Desktop Display Manager

Description

The vulnerability allows a local authenticated user to read and manipulate data.

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.

Mitigation
Install update from vendor's website.

Vulnerable software versions

sddm: 0.10.0 - 0.18.1

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External links
https://lists.opensuse.org/opensuse-security-announce/2020-11/msg00031.html
https://bugzilla.suse.com/show_bug.cgi?id=CVE-2020-28049
https://github.com/sddm/sddm/blob/v0.19.0/ChangeLog
https://github.com/sddm/sddm/releases
https://lists.debian.org/debian-lts-announce/2020/11/msg00009.html
https://www.debian.org/security/2020/dsa-4783

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.