CVE-2024-50131: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-50131 Overview

CVE-2024-50131 is a buffer boundary flaw [CWE-120] in the Linux kernel tracing subsystem. The vulnerability stems from an incorrect length check that fails to account for the NULL terminating byte when validating event string length. When strlen() returns a value equal to the maximum buffer length, no space remains for the NULL terminator, allowing out-of-bounds behavior. The kernel maintainers resolved the issue by adding a proper boundary check that returns failure when the string length matches the buffer capacity.

Critical Impact

A local authenticated attacker can trigger memory corruption in the kernel tracing path, leading to potential privilege escalation, information disclosure, or denial of service on affected Linux systems.

Affected Products

• Linux Kernel 6.12-rc1
• Linux Kernel 6.12-rc2 through 6.12-rc4
• Debian LTS distributions shipping affected kernel versions

Discovery Timeline

• 2024-11-05 - CVE-2024-50131 published to NVD
• 2026-05-12 - Last updated in NVD database

Technical Details for CVE-2024-50131

Vulnerability Analysis

The flaw resides in the Linux kernel tracing subsystem responsible for validating the length of event strings. The original validation logic used strlen() to measure incoming event names but compared the result against the buffer size without reserving a byte for the NULL terminator. Because strlen() excludes the terminating null byte from its return value, an event name whose length equals the maximum buffer size passes the check while leaving no room for \0. This off-by-one boundary condition produces unsafe writes when the kernel later treats the buffer as a C string.

Exploitation requires local access with low privileges. An attacker capable of interacting with the tracing interfaces can craft event names that satisfy the flawed length check, corrupting adjacent kernel memory. The local attack vector combined with high impact on confidentiality, integrity, and availability reflects the kernel-mode execution context.

Root Cause

The root cause is an input validation error in the event length check. The kernel code used strlen(name) > MAX_LEN instead of strlen(name) >= MAX_LEN, ignoring the byte required for null termination. The upstream patch corrects the comparison so that strings exactly matching the buffer length are rejected.

Attack Vector

The vulnerability is exploitable through local interfaces exposed by the tracing subsystem, such as tracefs or debugfs event creation paths. An attacker with sufficient access to write event definitions can pass a maximum-length string to trigger the boundary condition. Remote exploitation is not possible without prior local code execution. See the Linux Kernel Commit Log for the corrective patch details.

Detection Methods for CVE-2024-50131

Indicators of Compromise

• Unexpected kernel panics or oops messages referencing the tracing subsystem in dmesg output
• Anomalous writes to /sys/kernel/tracing/ or /sys/kernel/debug/tracing/ paths by non-administrative users
• Kernel memory corruption signatures captured by KASAN-enabled builds

Detection Strategies

• Audit kernel versions across the fleet and flag hosts running Linux Kernel 6.12-rc1 through 6.12-rc4 without the corrective commits
• Monitor for processes attempting to register tracing events with abnormally long name strings
• Correlate local privilege escalation alerts with prior access to tracing interfaces

Monitoring Recommendations

• Enable kernel audit rules on tracefs and debugfs mount points to log write activity
• Track setuid binary launches and unexpected root shells following tracing subsystem interaction
• Forward kernel logs to a centralized analytics platform for retrospective hunting on tracing-related faults

How to Mitigate CVE-2024-50131

Immediate Actions Required

• Apply the upstream kernel patches referenced in the vendor advisory URLs and rebuild affected kernels
• Update Debian systems using the Debian LTS Announcement and the March 2025 follow-up
• Industrial operators should review the Siemens Security Advisory for affected product guidance
• Restrict unprivileged user access to tracing interfaces until patches are deployed

Patch Information

The Linux kernel maintainers committed fixes across stable branches. See the patched commits including a14a075a14af, 0b6e2e22cb23, 5fd942598dde, b86b0d6eea20, and f4ed40d1c669.

Workarounds

• Unmount or restrict permissions on tracefs and debugfs to root-only access on production hosts
• Disable kernel tracing features in environments where they are not required by setting kernel boot parameters to disable ftrace
• Enforce least-privilege policies that prevent untrusted local users from interacting with kernel debug interfaces

# Restrict tracefs access to root only
mount -o remount,mode=700 /sys/kernel/tracing
chmod 700 /sys/kernel/debug/tracing