CVE-2023-28466: Linux Kernel Race Condition Vulnerability

CVE-2023-28466 Overview

CVE-2023-28466 is a race condition vulnerability in the Linux kernel's TLS (Transport Layer Security) implementation. The vulnerability exists in the do_tls_getsockopt function within net/tls/tls_main.c, where a missing lock_sock call creates a race condition that can lead to use-after-free or NULL pointer dereference conditions. This flaw affects Linux kernel versions through 6.2.6 and poses significant risk to systems relying on kernel-level TLS processing.

Critical Impact

Local attackers with low privileges can exploit this race condition to potentially achieve arbitrary code execution or cause denial of service through memory corruption.

Affected Products

• Linux Kernel (through version 6.2.6)
• NetApp H300S, H410C, H410S, H500S, H700S Storage Systems
• Debian Linux 10.0

Discovery Timeline

• 2023-03-16 - CVE CVE-2023-28466 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2023-28466

Vulnerability Analysis

This vulnerability stems from improper synchronization in the kernel's TLS socket option handling code. The do_tls_getsockopt function in net/tls/tls_main.c fails to acquire the socket lock before accessing socket-related data structures. In a multi-threaded environment, this missing synchronization primitive allows concurrent access to socket resources, creating a time-of-check time-of-use (TOCTOU) race condition.

When successfully exploited, the race condition can manifest in two ways: a use-after-free condition where memory is accessed after being freed by a concurrent operation, or a NULL pointer dereference when expected data structures are not properly initialized due to the race. Both conditions can lead to kernel memory corruption, potentially enabling privilege escalation or causing system crashes.

The vulnerability requires local access and specific timing conditions to exploit, but the potential for privilege escalation makes it a significant concern for multi-user systems and containerized environments where kernel isolation is critical.

Root Cause

The root cause is a missing lock_sock call in the do_tls_getsockopt function. Socket operations in the Linux kernel typically require holding the socket lock to prevent concurrent modifications to socket state. Without this lock, multiple threads can simultaneously access and modify socket-related data structures, leading to race conditions. The fix involves adding proper locking around the socket option retrieval code path to ensure atomicity of the operation.

Attack Vector

The attack requires local access to the system with the ability to create and manipulate TLS sockets. An attacker would need to trigger concurrent socket operations - specifically calling getsockopt() on a TLS socket while another thread performs operations that modify or free the socket's TLS context. The timing-sensitive nature of the exploit means that successful exploitation typically requires repeated attempts or precise control over thread scheduling.

The vulnerability is exploited through the following mechanism:

1. An attacker creates a TLS-enabled socket
2. Two or more threads are spawned targeting the same socket
3. One thread initiates a getsockopt() call to retrieve TLS parameters
4. Concurrently, another thread performs an operation that modifies or releases the TLS context
5. Due to the missing lock, the getsockopt() operation may access freed memory or a NULL pointer

Detection Methods for CVE-2023-28466

Indicators of Compromise

• Kernel panic or oops messages referencing do_tls_getsockopt or net/tls/tls_main.c in system logs
• Unexpected system crashes or reboots, particularly on systems with active TLS socket usage
• Kernel memory corruption warnings or use-after-free detection alerts from KASAN (Kernel Address Sanitizer)

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for TLS subsystem crashes or NULL pointer dereference errors
• Deploy kernel-level intrusion detection to identify anomalous socket operation patterns
• Use SentinelOne's kernel-level monitoring to detect exploitation attempts targeting TLS socket operations

Monitoring Recommendations

• Enable KASAN (Kernel Address Sanitizer) on development and testing systems to detect use-after-free conditions
• Configure audit rules to monitor processes making frequent concurrent socket operations
• Implement SentinelOne Singularity Platform for real-time detection of kernel exploitation attempts

How to Mitigate CVE-2023-28466

Immediate Actions Required

• Update the Linux kernel to a patched version that includes commit 49c47cc21b5b7a3d8deb18fc57b0aa2ab1286962
• For Debian 10 systems, apply security updates from the Debian LTS Announcement
• NetApp customers should review the NetApp Security Advisory for firmware updates

Patch Information

The vulnerability has been addressed in the upstream Linux kernel through commit 49c47cc21b5b7a3d8deb18fc57b0aa2ab1286962. This patch adds the necessary lock_sock and release_sock calls around the socket option retrieval code to prevent race conditions. The fix is available in the official Linux kernel repository and has been backported to various distribution kernels.

For detailed patch information, refer to the Linux Kernel Commit.

Workarounds

• Restrict local user access on affected systems to reduce the attack surface
• Consider disabling kernel TLS (kTLS) if not required by applications, reverting to userspace TLS implementations
• Implement container isolation and seccomp filters to limit socket system call access for untrusted workloads

# Check current kernel version
uname -r

# Verify if kTLS module is loaded
lsmod | grep tls

# To disable kTLS (if not required by applications)
modprobe -r tls
echo "blacklist tls" >> /etc/modprobe.d/blacklist.conf