Summary
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)
Fixed packages 2
| Release | Package | Fixed in |
|---|---|---|
| Ubuntu · 22.04 LTS 22.04:LTS | screen | 4.9.0-1ubuntu0.1 |
| Ubuntu · 24.04 LTS 24.04:LTS | screen | 4.9.1-1ubuntu1 |
Vulnerabilities 4
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Medium 6.5CVE-2023-24626 Public exploit
socket.c in GNU Screen through 4.9.0, when installed setuid or setgid (the default on platforms such as Arch Linux and …
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Medium 6.0
Temporary chown() of users' TTY to mode 0666 allows PTY hijacking in screen
For a short time they PTY is set to mode 666, allowing any user on the system to connect to the screen session.
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Medium 5.5
Screen has a TOCTOU race potentially allowing to send SIGHUP, SIGCONT to privileged processes when installed setuid-root
Screen version 5.0.0 and older version 4 releases have a TOCTOU race potentially allowing to send SIGHUP, SIGCONT to privileged processes when installed setuid-root.
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Low 3.3
Screen 5.0.0 and older versions allow file existence tests when installed setuid-root
A minor information leak when running Screen with setuid-root privileges allows unprivileged users to deduce information about a path that would otherwise not be available. Affected are older Screen versions, as well as version 5.0.0.