CVE-2025-21707
📋 TL;DR
This CVE describes an uninitialized variable vulnerability in the Linux kernel's MPTCP (Multipath TCP) implementation. Attackers could potentially exploit this to cause kernel memory corruption leading to crashes or privilege escalation. All Linux systems with MPTCP 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to denial of service, or potential privilege escalation allowing attackers to gain root access.
Likely Case
Kernel crash causing system instability and denial of service.
If Mitigated
No impact if MPTCP is disabled or the system is patched.
🎯 Exploit Status
Exploitation requires sending specially crafted MPTCP packets to trigger the uninitialized memory access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in kernel commits referenced in CVE
Vendor Advisory: https://git.kernel.org/stable/c/3a7fda57b0f91f7ea34476b165f91a92feb17c96
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing fixes. 2. Reboot system. 3. Verify kernel version with 'uname -r'.
🔧 Temporary Workarounds
Disable MPTCP
linuxDisable MPTCP functionality if not required
sysctl -w net.mptcp.enabled=0
echo 'net.mptcp.enabled = 0' >> /etc/sysctl.conf
sysctl -p
🧯 If You Can't Patch
- Disable MPTCP using sysctl commands
- Implement network filtering to block MPTCP traffic at firewall
🔍 How to Verify
Check if Vulnerable:
Check if MPTCP is enabled: sysctl net.mptcp.enabledCheck Version:
uname -rVerify Fix Applied:
Check kernel version after update and verify MPTCP is either disabled or patched📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- MPTCP-related error messages in dmesg
- System crash reports
Network Indicators:
- Unusual MPTCP traffic patterns
- MPTCP connection attempts to non-MPTCP services
SIEM Query:
source="kernel" AND ("MPTCP" OR "KMSAN" OR "uninit-value")🔗 References
- https://git.kernel.org/stable/c/3a7fda57b0f91f7ea34476b165f91a92feb17c96
- https://git.kernel.org/stable/c/3b5332d416d151a15742d1b16e7319368e3cc5c6
- https://git.kernel.org/stable/c/6169e942370b4b6f9442d35c51519bf6c346843b
- https://git.kernel.org/stable/c/7f6c72b8ef8130760710e337dc8fbe7263954884
- https://git.kernel.org/stable/c/ba0518f9e8688cd4fcb569e8df2a74874b4f3894
- https://git.kernel.org/stable/c/c86b000782daba926c627d2fa00c3f60a75e7472
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
