CVE-2024-26583: Linux Kernel Race Condition Vulnerability

CVE-2024-26583 Overview

CVE-2024-26583 is a race condition vulnerability in the Linux kernel's TLS (Transport Layer Security) subsystem. The flaw exists in the handling of asynchronous cryptographic operations where the submitting thread (which called recvmsg/sendmsg) may exit as soon as the async crypto handler calls complete(). Any code executing past that point risks accessing already freed memory, potentially leading to system instability or denial of service conditions.

Critical Impact

This race condition can cause use-after-free scenarios when async crypto handlers access memory after the submitting thread has exited and freed associated resources. Local attackers with low privileges could potentially trigger this vulnerability to cause system crashes.

Affected Products

• Linux Kernel (multiple versions)
• Fedora Linux distributions

Discovery Timeline

• 2024-02-21 - CVE-2024-26583 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2024-26583

Vulnerability Analysis

This vulnerability is classified as CWE-362 (Race Condition). The issue arises in the Linux kernel's TLS implementation where improper synchronization between asynchronous cryptographic operations and socket lifecycle management creates a race condition.

The core problem lies in the timing between when an async crypto handler signals completion and when the main thread exits. When a thread calls recvmsg() or sendmsg() on a TLS socket, the kernel may perform cryptographic operations asynchronously. If the async handler calls complete() to signal the operation is finished, the submitting thread may immediately exit and deallocate resources. However, if the async handler has additional code to execute after the complete() call, it may attempt to access memory that has already been freed.

The fix implements a reference counting approach where the main thread holds an extra reference, allowing synchronization to rely solely on the atomic reference counter rather than additional locking mechanisms and flags. This eliminates the need to reinitialize the completion structure, providing tighter control over when completion fires.

Root Cause

The root cause is a synchronization deficiency in the TLS subsystem's async crypto handling path. The original implementation did not properly account for the scenario where the submitting thread could exit immediately upon receiving the completion signal, leaving the async handler to potentially access freed data structures. The lack of proper reference counting between the async crypto handler and the socket lifecycle allowed this timing-sensitive race to occur.

Attack Vector

The vulnerability requires local access to the system with low privileges. An attacker would need to:

1. Establish a TLS socket connection that triggers asynchronous cryptographic operations
2. Manipulate the timing of socket operations (recvmsg/sendmsg) and socket closure
3. Trigger the race condition where the async crypto handler accesses freed memory after the submitting thread exits

Due to the high attack complexity (requiring precise timing manipulation), exploitation is difficult but could result in denial of service through system crashes or kernel panic conditions. The attack does not require user interaction.

The vulnerability mechanism involves the TLS subsystem's async crypto completion path where improper synchronization allows memory to be accessed after deallocation. The fix introduces an extra reference held by the main thread, ensuring proper synchronization through atomic reference counting rather than relying on completion flags and additional locking. For technical implementation details, see the kernel commit 6209319b.

Detection Methods for CVE-2024-26583

Indicators of Compromise

• Kernel panic or crash logs referencing TLS subsystem functions or async crypto handlers
• Unexpected system instability when applications heavily utilize TLS connections with async crypto operations
• Memory corruption errors in kernel logs related to socket operations
• Crash dumps showing use-after-free patterns in TLS-related kernel code paths

Detection Strategies

• Monitor kernel logs for panic events or memory corruption errors involving the TLS subsystem (net/tls/ module)
• Implement kernel tracing to detect anomalous behavior in recvmsg/sendmsg syscalls on TLS sockets
• Use kernel debugging tools (KASAN) to detect use-after-free conditions during TLS operations
• Deploy endpoint detection solutions capable of monitoring kernel-level race conditions

Monitoring Recommendations

• Enable kernel crash dump collection to capture diagnostic information if the vulnerability is triggered
• Monitor system stability metrics for unexplained crashes or restarts, particularly on servers with high TLS traffic
• Implement centralized logging for kernel messages across affected systems
• Use SentinelOne's Singularity platform to monitor for kernel-level anomalies and potential exploitation attempts

How to Mitigate CVE-2024-26583

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for this race condition
• Review and prioritize patching for systems that handle significant TLS traffic or untrusted network connections
• Monitor affected systems for signs of instability until patches can be applied
• Consider restricting local access to critical systems where kernel updates cannot be immediately deployed

Patch Information

Multiple kernel commits have been released to address this vulnerability. The fix implements proper reference counting where the main thread holds an extra reference, allowing synchronization through atomic reference counting. This approach eliminates the need for additional locking mechanisms and flags while providing tighter control over completion timing.

Apply the appropriate patch based on your kernel version:

• Kernel Commit 6209319b
• Kernel Commit 7a3ca06d
• Kernel Commit 86dc27ee
• Kernel Commit aec79619

Fedora users should refer to the Fedora Package Announcement for distribution-specific updates.

Workarounds

• Limit local system access to trusted users where possible, as exploitation requires local access
• Monitor systems with elevated logging to detect potential exploitation attempts
• Consider temporarily disabling TLS hardware acceleration (async crypto) if the race condition is being actively exploited
• Implement network segmentation to reduce exposure of vulnerable systems to potential attackers

# Check current kernel version and TLS module status
uname -r
lsmod | grep tls

# Update kernel on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade linux-image-$(uname -r)

# Update kernel on RHEL/CentOS/Fedora systems
sudo dnf update kernel

# Reboot to apply new kernel
sudo reboot