CVE-2025-71086: Linux Kernel Use-After-Free Vulnerability

CVE-2025-71086 Overview

A vulnerability has been identified in the Linux kernel's ROSE (Radio Oriented Satellite Equipment) network protocol implementation. The flaw exists in the rose_kill_by_device() function, which is responsible for disconnecting sockets bound to a network device being brought down. Due to an incorrect loop index variable, the function may access uninitialized array entries or perform out-of-bounds reads, potentially leading to invalid socket pointer dereferences and reference leaks.

Critical Impact

This vulnerability can cause kernel crashes, memory corruption, or system instability when network interfaces using the ROSE protocol are administratively brought down.

Affected Products

• Linux kernel (versions with ROSE protocol support)
• Systems with CONFIG_ROSE enabled
• Amateur radio/packet radio systems using ROSE protocol

Discovery Timeline

• 2026-01-13 - CVE CVE-2025-71086 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-71086

Vulnerability Analysis

The vulnerability resides in the rose_kill_by_device() function within the Linux kernel's ROSE networking subsystem. This function is invoked when a network device is being taken down and needs to disconnect all associated sockets. The function collects socket references into a local array and subsequently iterates over them to perform the disconnection.

The critical flaw is a programming error where the loop that processes the collected sockets uses the wrong index variable. Instead of using the loop iterator i to access array[i], the code incorrectly uses array[cnt], where cnt is the count of collected sockets. This leads to two potential problematic scenarios: when cnt is less than the array size, an uninitialized entry is read; when cnt equals the array size, an out-of-bounds read occurs.

Root Cause

The root cause is a simple but critical indexing error in the socket processing loop. The developer mistakenly used the counter variable cnt instead of the loop iterator variable i when accessing array elements during the socket disconnection phase. This type of error is a common programming mistake that can have severe consequences in kernel-level code where memory safety is paramount.

Attack Vector

The vulnerability is triggered when a network interface with ROSE protocol bindings is administratively brought down. While this typically requires local access or elevated privileges to manage network interfaces, the consequences include:

• Invalid memory reads from uninitialized or out-of-bounds array positions
• Dereferencing of invalid socket pointers leading to kernel crashes
• Reference count leaks via sock_hold() calls that are never balanced with corresponding releases
• Potential kernel panic or system destabilization

The fix involves changing the array index from cnt to i in the processing loop, ensuring that each collected socket is properly accessed and processed. Multiple kernel git commits have been issued to address this vulnerability across various kernel branches.

Detection Methods for CVE-2025-71086

Indicators of Compromise

• Kernel panic or oops messages referencing rose_kill_by_device() in the call stack
• System crashes or freezes when bringing down network interfaces with ROSE protocol bindings
• Kernel log messages indicating invalid memory access in the net/rose subsystem
• Unexpected system instability during network reconfiguration events

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for ROSE protocol-related errors
• Implement kernel crash dump analysis to identify the vulnerable function in stack traces
• Use kernel debugging tools like KASAN (Kernel Address Sanitizer) to detect memory access violations
• Deploy SentinelOne Singularity Platform for real-time kernel anomaly detection

Monitoring Recommendations

• Enable kernel auditing for network device state changes
• Configure crash dump collection to capture kernel panics for forensic analysis
• Monitor system stability metrics during network interface operations
• Implement automated alerting for kernel-level memory errors

How to Mitigate CVE-2025-71086

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix
• If immediate patching is not possible, consider disabling the ROSE protocol module if not required
• Monitor systems with ROSE protocol enabled for signs of instability
• Plan maintenance windows for kernel updates on production systems

Patch Information

The vulnerability has been addressed in multiple kernel stable branches. The fix changes the incorrect array index from cnt to i in the socket processing loop. Patches are available via the following kernel git commits:

• Kernel Git Commit 1418c12
• Kernel Git Commit 6595beb
• Kernel Git Commit 92d900a
• Kernel Git Commit 9f6185a
• Kernel Git Commit b409ba9

Workarounds

• Disable the ROSE protocol module if not required: modprobe -r rose
• Blacklist the ROSE module to prevent automatic loading: add blacklist rose to /etc/modprobe.d/blacklist.conf
• Avoid bringing down network interfaces with active ROSE bindings until patched
• Implement network change controls to minimize interface state changes on vulnerable systems

# Disable ROSE protocol module if not required
modprobe -r rose

# Blacklist ROSE module to prevent automatic loading
echo "blacklist rose" >> /etc/modprobe.d/blacklist.conf

# Verify ROSE module is not loaded
lsmod | grep rose