CVE-2023-26545 Overview
CVE-2023-26545 is a double free vulnerability in the Linux kernel's MPLS (Multiprotocol Label Switching) subsystem, specifically within the net/mpls/af_mpls.c file. The vulnerability occurs during the renaming of a network device when an allocation failure happens while registering the sysctl table under a new location. This memory corruption issue can lead to system instability and potential denial of service conditions on affected Linux systems.
Critical Impact
A local attacker with low privileges could exploit this double free condition to cause kernel memory corruption, potentially leading to system crashes and denial of service on affected Linux systems and appliances.
Affected Products
- Linux Kernel versions before 6.1.13
- Debian Linux 10.0
- NetApp H300S/H500S/H700S/H410S/H410C Firmware
Discovery Timeline
- 2023-02-25 - CVE-2023-26545 published to NVD
- 2025-06-25 - Last updated in NVD database
Technical Details for CVE-2023-26545
Vulnerability Analysis
This double free vulnerability (CWE-415) exists in the MPLS network subsystem of the Linux kernel. The flaw is triggered during the device rename operation when a memory allocation fails while attempting to register a sysctl table at a new location. When this allocation failure occurs, the error handling path incorrectly frees memory that may have already been freed or will be freed again later, resulting in a classic double free condition.
The vulnerability requires local access to exploit, and while it has high complexity requirements, it can be triggered by a user with low privileges. Successful exploitation results in a denial of service condition through system instability or kernel panic.
Root Cause
The root cause of CVE-2023-26545 lies in improper error handling within the MPLS device management code. When a device is renamed and the system attempts to register a new sysctl table, an allocation failure leaves a stale pointer in the mdev->sysctl structure. This stale pointer is not properly nullified in the error path, leading to a situation where the same memory region can be freed multiple times when subsequent cleanup operations reference this dangling pointer.
Attack Vector
The attack requires local access to the system with the ability to trigger network device rename operations. An attacker would need to create conditions that cause memory allocation failures during the sysctl table registration process. This could potentially be achieved through:
- Exhausting system memory resources to force allocation failures
- Triggering rapid device rename operations under memory pressure
- Exploiting race conditions in the error handling path
The following patch demonstrates the fix applied to address the stale pointer issue:
free:
kfree(table);
out:
+ mdev->sysctl = NULL;
return -ENOBUFS;
}
Source: GitHub Linux Commit fda6c89fe3
The fix properly sets mdev->sysctl to NULL in the error path before returning, preventing the stale pointer from being dereferenced and freed again in subsequent cleanup operations.
Detection Methods for CVE-2023-26545
Indicators of Compromise
- Unexpected kernel panics or system crashes related to MPLS or network device operations
- Kernel log messages indicating double free conditions in net/mpls/af_mpls.c
- Memory corruption errors occurring during network interface rename operations
- System instability when performing MPLS-related network configuration changes
Detection Strategies
- Monitor kernel logs for KASAN (Kernel Address Sanitizer) reports indicating double free detection in MPLS subsystem
- Implement kernel debugging features to detect use-after-free and double free conditions
- Deploy endpoint detection solutions capable of monitoring kernel-level memory corruption events
- Use SentinelOne's behavioral AI to detect anomalous system behavior patterns associated with kernel exploitation
Monitoring Recommendations
- Enable kernel auditing for network namespace and device rename operations
- Configure KASAN or KMSAN on development and staging systems to catch memory safety violations
- Monitor for unusual memory allocation failure patterns that could indicate exploitation attempts
- Track system stability metrics and correlate crashes with network configuration changes
How to Mitigate CVE-2023-26545
Immediate Actions Required
- Update Linux kernel to version 6.1.13 or later to receive the security fix
- Apply vendor-specific patches from Debian, NetApp, and other affected vendors
- Restrict local access to systems where kernel updates cannot be immediately applied
- Monitor affected systems for signs of exploitation or instability
Patch Information
The vulnerability has been fixed in Linux kernel version 6.1.13 and later. The fix is available through commit fda6c89fe3d9aca073495a664e1d5aea28cd4377 in the upstream Linux kernel repository.
Vendor Resources:
- GitHub Linux Commit fda6c89fe3
- Linux 6.1.13 ChangeLog
- Debian LTS Announcement May 2023
- NetApp Security Advisory ntap-20230316-0009
Workarounds
- Limit local access to affected systems to trusted users only
- Disable MPLS functionality if not required by removing the mpls_router and mpls_iptunnel kernel modules
- Implement strict resource limits to reduce the likelihood of allocation failures that trigger the vulnerability
- Deploy additional monitoring to detect abnormal system behavior during network device operations
# Disable MPLS modules if not required
modprobe -r mpls_iptunnel
modprobe -r mpls_router
echo "blacklist mpls_router" >> /etc/modprobe.d/blacklist-mpls.conf
echo "blacklist mpls_iptunnel" >> /etc/modprobe.d/blacklist-mpls.conf
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
