CVE-2025-37959
📋 TL;DR
A Linux kernel vulnerability in the bpf_redirect_peer function fails to properly scrub packet metadata when redirecting packets between network namespaces. This allows sensitive network state information (like XFRM decryption state) to leak across namespace boundaries, potentially causing packet drops or other unexpected behavior. Systems using BPF programs with bpf_redirect_peer across network namespaces are affected, particularly those using container networking solutions like Cilium.
💻 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 →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
Information leakage between network namespaces could enable privilege escalation, container escape, or bypass of network security policies by exposing internal network state across namespace boundaries.
Likely Case
Unexpected packet drops and network connectivity issues in containerized environments, particularly affecting IPsec traffic and systems using Cilium for networking.
If Mitigated
Minor network performance impact or packet drops in specific container networking scenarios, but no security compromise if proper network segmentation exists.
🎯 Exploit Status
Exploitation requires ability to load BPF programs and manipulate network namespaces, typically requiring elevated privileges. The primary impact observed is denial of service through packet drops.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel patches available in stable branches (commits: 355b0526336c0bf2bf7feaca033568ede524f763, 9e15ef33ba39fb6d9d1f51445957f16983a9437a, b37e54259cab4f78b53953d6f6268b85f07bef3e, c4327229948879814229b46aa26a750718888503, de1067cc8cf0e8c11ae20cbe5c467aef19d04ded)
Vendor Advisory: https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. For distributions: Use package manager to update kernel package. 3. Reboot system to load new kernel. 4. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable bpf_redirect_peer usage
linuxAvoid using bpf_redirect_peer in BPF programs that cross network namespace boundaries
Review and modify BPF programs to avoid bpf_redirect_peer across namespaces
Use alternative redirection methods like bpf_redirect
Network namespace isolation
linuxEnsure strict network namespace separation and avoid unnecessary cross-namespace packet redirection
Review container networking configurations
Avoid sharing network interfaces between namespaces when possible
🧯 If You Can't Patch
- Monitor for unexpected packet drops in container networking, particularly IPsec traffic
- Implement network monitoring to detect abnormal cross-namespace traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check if system uses BPF programs with bpf_redirect_peer across network namespaces. Review kernel version against patched releases.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the patch commits. Test container networking with IPsec to ensure no unexpected packet drops.📡 Detection & Monitoring
Log Indicators:
- Unexpected packet drops with SKB_DROP_REASON_XFRM_POLICY
- Network connectivity issues between containers
- Kernel logs showing XFRM policy mismatches
Network Indicators:
- Increased packet loss in container networking
- IPsec traffic failures in containerized environments
SIEM Query:
kernel: "SKB_DROP_REASON_XFRM_POLICY" OR "LINUX_MIB_XFRMINNOPOLS" OR container_network: packet_drop_rate > threshold🔗 References
- https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763
- https://git.kernel.org/stable/c/9e15ef33ba39fb6d9d1f51445957f16983a9437a
- https://git.kernel.org/stable/c/b37e54259cab4f78b53953d6f6268b85f07bef3e
- https://git.kernel.org/stable/c/c4327229948879814229b46aa26a750718888503
- https://git.kernel.org/stable/c/de1067cc8cf0e8c11ae20cbe5c467aef19d04ded
- https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html
