CVE-2026-31423
Divide-by-Zero Vulnerability in Linux Kernel HFSC Scheduler
Publication date: 2026-04-13
Last updated on: 2026-04-18
Assigner: kernel.org
Description
Description
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability causes a divide-by-zero kernel oops in the Linux kernel's HFSC scheduler code path. Detection would typically involve monitoring for kernel oops or crash messages related to the HFSC scheduler, specifically messages mentioning "Oops: divide error" and the function "rtsc_min" in net/sched/sch_hfsc.c.
You can check your system logs (e.g., using dmesg or journalctl) for such kernel oops messages:
- dmesg | grep -i 'Oops: divide error'
- journalctl -k | grep -i 'rtsc_min'
Additionally, monitoring for crashes or instability when using the HFSC queuing discipline in network traffic control (tc) may indicate the presence of this issue.
Can you explain this vulnerability to me?
This vulnerability exists in the Linux kernel's network scheduler component, specifically in the sch_hfsc module. It involves a divide-by-zero error in the function rtsc_min().
The issue arises because a 64-bit difference value is stored in a 32-bit variable, causing truncation. When the difference equals 2^32, the truncated value becomes zero, which is then used as a divisor, leading to a divide-by-zero error and a kernel crash (oops).
The fix involves widening the variable to 64 bits and using a 64-bit division function to prevent truncation and the resulting divide-by-zero.
How can this vulnerability impact me? :
This vulnerability can cause the Linux kernel to crash due to a divide-by-zero error in the network scheduler. Such a crash can lead to denial of service (DoS) conditions, disrupting network traffic management and potentially affecting system stability and availability.
What immediate steps should I take to mitigate this vulnerability?
The vulnerability is fixed by widening the variable used as a divisor and replacing the division function to prevent divide-by-zero errors in the HFSC scheduler code.
Immediate mitigation steps include:
- Update your Linux kernel to a version that includes the fix for this vulnerability.
- If updating immediately is not possible, avoid using the HFSC queuing discipline (sch_hfsc) in your network traffic control configurations to prevent triggering the vulnerable code path.
- Monitor system logs for any kernel oops related to this issue and plan for a kernel upgrade as soon as possible.