CVE-2025-31160: atop Denial of Service Vulnerability

CVE-2025-31160 Overview

CVE-2025-31160 is a denial of service vulnerability affecting the atop Linux process and system resource monitor through version 2.11.0. The flaw allows local users to cause a denial of service condition, typically manifesting as an assertion failure and application exit, by running certain types of unprivileged processes while a different user runs atop. The vulnerability may also have unspecified additional impact beyond service disruption.

Critical Impact

Local unprivileged users can crash the atop monitoring tool used by system administrators, potentially disrupting system monitoring and performance analysis capabilities on affected Linux systems.

Affected Products

• atop versions through 2.11.0
• Linux systems running vulnerable atop installations
• Debian-based distributions with affected atop packages

Discovery Timeline

• 2025-03-26 - CVE-2025-31160 published to NVD
• 2025-04-07 - Last updated in NVD database

Technical Details for CVE-2025-31160

Vulnerability Analysis

This vulnerability is classified under CWE-617 (Reachable Assertion), which describes a condition where an assertion designed to be unreachable during normal operation can be triggered by an attacker. In the case of atop, the assertion failure occurs when the monitoring tool encounters unexpected process states while parsing system information.

The vulnerability requires local access to exploit, meaning an attacker must have some form of access to the target system. The exploitation complexity is considered high because it requires specific timing conditions where an unprivileged user runs certain process types concurrently with another user's atop session. While the confidentiality and integrity impact is none, the availability impact allows disruption of the monitoring service.

Root Cause

The root cause of CVE-2025-31160 lies in atop's handling of process data parsing from the /proc filesystem. When atop reads process information while certain types of unprivileged processes are executing, the tool encounters unexpected data states that trigger an internal assertion check. This assertion, rather than gracefully handling the unexpected condition, causes the application to terminate immediately.

The assertion mechanism, while useful for debugging during development, should not be exposed in production code paths where untrusted input (in this case, the dynamic state of system processes) can trigger termination. According to analysis discussed on the Bismuth Blog, the issue relates to how atop handles race conditions when reading process metadata.

Attack Vector

The attack requires local access to the system where atop is running. An attacker can exploit this vulnerability by:

1. Identifying when a privileged user or automated system runs atop for system monitoring
2. Launching specific unprivileged processes designed to create the race condition
3. Causing the atop process to encounter an assertion failure and crash

Since the attack only requires unprivileged access, any local user on a multi-user system could potentially disrupt monitoring operations. The vulnerability is particularly relevant in shared hosting environments or systems where multiple users have shell access.

Detailed technical analysis and discussion of the bug can be found in the Rachel By The Bay Article and subsequent community discussion threads.

Detection Methods for CVE-2025-31160

Indicators of Compromise

• Unexpected termination of atop processes with assertion failure messages in system logs
• Repeated crashes of atop daemon or interactive sessions
• Core dumps from atop containing assertion failure stack traces
• Suspicious process activity from unprivileged users coinciding with atop crashes

Detection Strategies

• Monitor system logs for atop assertion failure messages or abnormal termination signals
• Implement process monitoring to detect unexpected atop restarts or crashes
• Review audit logs for patterns of process creation that correlate with atop service disruptions
• Deploy file integrity monitoring on atop binary and configuration files

Monitoring Recommendations

• Configure log aggregation to alert on atop crash patterns across monitored systems
• Implement watchdog mechanisms to automatically restart atop services after crashes
• Monitor for unusual process spawning activity from unprivileged accounts
• Review system resource usage patterns for anomalies around atop crash events

How to Mitigate CVE-2025-31160

Immediate Actions Required

• Update atop to a patched version when available from your distribution
• Review which users have local access to systems running atop for monitoring
• Consider restricting access to systems where atop is used for critical monitoring
• Implement process restart mechanisms to maintain monitoring continuity

Patch Information

Security updates have been released for affected distributions. Debian users should refer to the Debian LTS Announcement for patch details. For other distributions, monitor the official atop GitHub repository for upstream fixes.

System administrators should apply vendor-provided patches through standard package management:

# For Debian/Ubuntu systems
sudo apt update && sudo apt upgrade atop

# For RHEL/CentOS systems
sudo dnf update atop

Workarounds

• Restrict local shell access to systems where atop is used for critical monitoring functions
• Run atop in isolated environments or containers where possible to limit exposure
• Implement process isolation using namespaces to separate atop from untrusted user processes
• Consider alternative monitoring tools temporarily if atop availability is critical

# Configuration example
# Verify current atop version
atop -V

# Check for available updates
apt-cache policy atop

# After patching, verify the fix
atop -V