USN-7978-1: GNU Screen vulnerabilities

USN-7978-1: GNU Screen vulnerabilities
Publication date: 26 January 2026
Overview: Several security issues were fixed in GNU Screen.

Packages
screen - terminal multiplexer with VT100/ANSI terminal emulation

Details
It was discovered that GNU Screen incorrectly handled signals when setuid
or setgid privileges were being used, which is not the default in Ubuntu.
A local attacker could use this issue to send privileged signals, possibly
leading to a denial of service. This issue only affected Ubuntu 22.04 LTS.
(CVE-2023-24626)

It was discovered that GNU Screen incorrectly handled PTY permissions. A
local attacker could possibly use this issue to connect to an unauthorized
screen session. (CVE-2025-46802)

It was discovered that GNU Screen incorrectly handled file access when
setuid privileges were being used, which is not the default in Ubuntu. A
local attacker could use this issue to deduce information about certain
file paths. (CVE-2025-46804)

It was discovered that GNU Screen incorrectly handled signals when setuid
privileges were being used, which is not the default in Ubuntu. A local
attacker could use this issue to send privileged signals, possibly leading
to a denial of service. (CVE-2025-46805)

Update instructions
In general, a standard system update will make all the necessary changes.

The problem can be corrected by updating your system to the following package versions:

• 24.04 LTS noble screen – 4.9.1-1ubuntu1
• 22.04 LTS jammy screen – 4.9.0-1ubuntu0.1