CVE-2025-39673
📋 TL;DR
A race condition vulnerability in the Linux kernel's PPP implementation could allow local attackers to cause a kernel panic (system crash) or potentially execute arbitrary code. This affects systems using PPP (Point-to-Point Protocol) networking, typically in embedded devices, routers, or servers with PPP connections. Attackers need local access to exploit this vulnerability.
💻 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 →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 to kernel-level code execution if combined with other vulnerabilities.
Likely Case
Local denial of service through kernel panic when PPP channels are manipulated concurrently.
If Mitigated
Minimal impact with proper access controls preventing local attackers from manipulating PPP interfaces.
🎯 Exploit Status
Requires local access and timing race conditions. Exploitation requires manipulating PPP channels while ppp_fill_forward_path() is executing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 0417adf367a0af11adf7ace849af4638cfb573f7, 0f1630be6fcca3f0c63e4b242ad202e5cde28a40, 94731cc551e29511d85aa8dec61a6c071b1f2430, 9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7, ca18d751bcc9faf5b7e82e9fae1223d103928181
Vendor Advisory: https://git.kernel.org/stable/c/0417adf367a0af11adf7ace849af4638cfb573f7
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify PPP functionality still works if needed.
🔧 Temporary Workarounds
Disable PPP module
LinuxRemove or blacklist PPP kernel module if not needed
echo 'blacklist ppp_generic' >> /etc/modprobe.d/blacklist.conf
rmmod ppp_generic
🧯 If You Can't Patch
- Restrict local user access to prevent malicious users from exploiting race conditions
- Disable PPP networking if not required for system functionality
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if PPP module is loaded: lsmod | grep pppCheck Version:
uname -rVerify Fix Applied:
Check kernel version contains fix commits or is newer than patched versions📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- PPP-related crash reports
Network Indicators:
- Unexpected PPP disconnections or interface failures
SIEM Query:
source="kernel" AND ("panic" OR "Oops") AND "ppp"🔗 References
- https://git.kernel.org/stable/c/0417adf367a0af11adf7ace849af4638cfb573f7
- https://git.kernel.org/stable/c/0f1630be6fcca3f0c63e4b242ad202e5cde28a40
- https://git.kernel.org/stable/c/94731cc551e29511d85aa8dec61a6c071b1f2430
- https://git.kernel.org/stable/c/9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7
- https://git.kernel.org/stable/c/ca18d751bcc9faf5b7e82e9fae1223d103928181
- https://git.kernel.org/stable/c/f97f6475fdcb3c28ff3c55cc4b7bde632119ec08
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
