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[USN-7978-1] GNU Screen vulnerabilities

Posted on 27 January 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-7978-1
January 26, 2026

screen vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

Several security issues were fixed in GNU Screen.

Software Description:
- 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:

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

Ubuntu 24.04 LTS
screen 4.9.1-1ubuntu1

Ubuntu 22.04 LTS
screen 4.9.0-1ubuntu0.1

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

References:
https://ubuntu.com/security/notices/USN-7978-1
CVE-2023-24626, CVE-2025-46802, CVE-2025-46804, CVE-2025-46805

Package Information:
https://launchpad.net/ubuntu/+source/screen/4.9.1-1ubuntu1
https://launchpad.net/ubuntu/+source/screen/4.9.0-1ubuntu0.1

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