tmux Use-After-Free Vulnerability Enables Local Denial of Service
Ubuntu has released a security update addressing a use-after-free flaw in tmux's image cleanup routine. A local attacker could exploit this vulnerability to crash the terminal multiplexer, disrupting user sessions.
TL;DR
- tmux contains a use-after-free vulnerability in image cleanup logic
- Local attackers can trigger a denial of service by crashing tmux
- Ubuntu Security Notice USN-8428-1 provides the patch
- Affects systems where tmux is deployed for terminal management
- Update recommended for all tmux installations on Ubuntu systems
Ubuntu has disclosed a use-after-free vulnerability in tmux, a widely-used terminal multiplexer that enables users to manage multiple terminal sessions within a single window. The flaw resides in the application's image cleanup routine, where improper memory handling creates an exploitable condition.
A local attacker with access to a system running vulnerable tmux can trigger this vulnerability to cause the application to crash, resulting in a denial of service. While the immediate impact is limited to availability rather than data compromise, disruption of terminal sessions can affect system administration workflows and automation tasks.
The vulnerability underscores the importance of maintaining up-to-date software dependencies, particularly for tools that operate at the system level. Organizations relying on tmux for remote session management should prioritize applying the security patch.
Technical Details
- Vulnerability type: use-after-free memory error in image cleanup code
- Attack vector: local, requiring attacker presence on the target system
- Impact: denial of service through application crash
- No remote exploitation or privilege escalation reported
- Affects tmux process and user sessions dependent on it
Remediation and Best Practices
- Apply Ubuntu Security Notice USN-8428-1 immediately to affected systems
- Verify tmux version post-patch to confirm vulnerability closure
- Monitor system logs for unexpected tmux crashes or restarts
- Restrict local system access to trusted users where feasible
- Consider session management policies that limit tmux exposure in multi-tenant environments
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