CVE-2025-38177
📋 TL;DR
This CVE addresses a non-idempotent function in the Linux kernel's HFSC (Hierarchical Fair Service Curve) queuing discipline that could cause kernel instability. The vulnerability affects Linux systems using HFSC for network traffic shaping. Attackers could potentially trigger denial of service conditions or kernel crashes by exploiting the improper state management.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic or system crash leading to complete denial of service, requiring physical or remote console access to restore functionality.
Likely Case
Network instability, packet loss, or degraded performance in systems using HFSC queuing discipline.
If Mitigated
Minor performance impact or no noticeable effect if HFSC is not actively used or properly configured.
🎯 Exploit Status
Exploitation requires ability to manipulate network queuing, typically requiring local access or specific network configuration. No known active exploitation in the wild.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple stable kernel versions with commit hashes provided in references
Vendor Advisory: https://git.kernel.org/stable/c/0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. For custom kernels, apply commits from provided git references. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable HFSC queuing discipline
linuxSwitch from HFSC to alternative queuing discipline like pfifo_fast or fq_codel
tc qdisc del dev <interface> root
tc qdisc add dev <interface> root pfifo_fast
🧯 If You Can't Patch
- Disable HFSC queuing discipline on all network interfaces
- Implement network segmentation to limit potential attack surface
🔍 How to Verify
Check if Vulnerable:
Check if HFSC is in use: tc qdisc show | grep hfscCheck Version:
uname -rVerify Fix Applied:
Check kernel version after update: uname -r and verify it matches patched version from distribution📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Network subsystem errors in dmesg
- Unexpected system reboots
Network Indicators:
- Sudden network performance degradation
- Packet loss on HFSC-configured interfaces
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "HFSC" OR "qdisc")🔗 References
- https://git.kernel.org/stable/c/0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87
- https://git.kernel.org/stable/c/51eb3b65544c9efd6a1026889ee5fb5aa62da3bb
- https://git.kernel.org/stable/c/72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7
- https://git.kernel.org/stable/c/9030a91235ae4845ec71902c3e0cecfc9ed1f2df
- https://git.kernel.org/stable/c/9a5fd5c2f4d4afdd5e405083ee53e0789ce76956
- https://git.kernel.org/stable/c/a5efc95a33bd4fcb879250852828cc58c7862970
- https://git.kernel.org/stable/c/c1175c4ad01dbc9c979d099861fa90a754f72059
- https://git.kernel.org/stable/c/d06476714d2819b550e0cc39222347e2c8941c9d
- https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
