Privilege Escalation Vulnerability in Screen Package
Summary
DEBIAN-CVE-2025-46802: For a short time they PTY is set to mode 666, allowing any user on the system to connect to the screen session. Affects screen versions < 4.9.1-3. Fixed in 4.9.1-3. How to fix ↓
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Background
The Screen package is a terminal multiplexer that allows users to manage multiple terminal sessions from a single interface. It is widely used in Unix-like operating systems for its ability to detach and reattach sessions, making it invaluable for remote work and long-running processes. However, a recent vulnerability has been identified that could allow unauthorized users to access screen sessions.
Vulnerability Detail
The vulnerability arises from a temporary misconfiguration where the pseudo-terminal (PTY) is set to mode 666. This mode permits any user on the system to connect to the screen session, potentially leading to unauthorized access to sensitive information or control over the session. This issue is particularly concerning in multi-user environments where privacy and security are paramount.
How To Fix
Minimum fixed version
4.9.1-3
This is the first release that contains the fix.
sudo apt-get install --only-upgrade screenTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can restrict access to the screen sessions by changing the permissions of the PTY or by using alternative session management tools until the package is updated.
Conclusion
The identified vulnerability in the Screen package poses a significant risk by allowing unauthorized access to screen sessions. Users are strongly advised to update to the patched version 4.9.1-3 to mitigate this risk. For ongoing monitoring of vulnerabilities, tools like Vulert can provide real-time alerts and insights.
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FAQ
The vulnerability allows any user on the system to connect to a screen session due to the PTY being set to mode 666 temporarily.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected.
The risks include unauthorized access to sensitive information and control over the screen sessions, which could lead to data breaches or system compromise.
Yes, the patched version of the Screen package is 4.9.1-3. Updating to this version will resolve the vulnerability.
If immediate updates are not possible, consider using alternative session management tools or restrict access to screen sessions as a temporary measure.
References
Related vulnerabilities
Recent vulnerabilities recorded for screen.
