CVE-2025-21759
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's IPv6 multicast implementation. Attackers could potentially exploit this to cause kernel crashes or execute arbitrary code with kernel privileges. Systems running vulnerable Linux kernel versions with IPv6 enabled are affected.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash, or potential arbitrary code execution with kernel privileges resulting in complete system compromise.
Likely Case
Kernel crash leading to denial of service and system instability.
If Mitigated
Minimal impact if proper network segmentation and access controls prevent attackers from reaching vulnerable systems.
🎯 Exploit Status
Exploitation requires network access and ability to send IPv6 multicast packets. No public exploit code is currently available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in stable kernel trees (commits: 087c1faa594fa07a66933d750c0b2610aa1a2946, 0bf8e2f3768629d437a32cb824149e6e98254381, 81b25a07ebf53f9ef4ca8f3d96a8ddb94561dd5a, 8e92d6a413feaf968a33f0b439ecf27404407458)
Vendor Advisory: https://git.kernel.org/stable/c/087c1faa594fa07a66933d750c0b2610aa1a2946
Restart Required: Yes
Instructions:
1. Update to a patched kernel version from your distribution's repositories. 2. Reboot the system to load the new kernel. 3. Verify the kernel version after reboot.
🔧 Temporary Workarounds
Disable IPv6
allCompletely disable IPv6 functionality to prevent exploitation.
echo 'net.ipv6.conf.all.disable_ipv6 = 1' >> /etc/sysctl.conf
echo 'net.ipv6.conf.default.disable_ipv6 = 1' >> /etc/sysctl.conf
sysctl -p
Block IPv6 multicast traffic
allUse firewall rules to block incoming IPv6 multicast packets.
ip6tables -A INPUT -d ff00::/8 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to limit access to vulnerable systems
- Deploy network monitoring to detect suspicious IPv6 multicast traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with patched versions from your distribution's security advisories.Check Version:
uname -rVerify Fix Applied:
Verify kernel version matches patched version and test IPv6 multicast functionality remains operational.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/messages or dmesg
- Unexpected system crashes or reboots
Network Indicators:
- Unusual IPv6 multicast traffic patterns
- Spike in IGMPv6 packets from unexpected sources
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "general protection fault")