CVE-2025-39900
BaseFortify
Publication date: 2025-10-01
Last updated on: 2025-12-12
Assigner: kernel.org
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | From 6.12 (inc) to 6.12.46 (exc) |
| linux | linux_kernel | From 6.13 (inc) to 6.16.6 (exc) |
| linux | linux_kernel | 6.17 |
| linux | linux_kernel | 6.17 |
| linux | linux_kernel | 6.17 |
| linux | linux_kernel | 6.17 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-NVD-CWE-noinfo |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is in the Linux kernel's net_sched component, specifically in the gen_estimator's est_timer() function. When the kernel is configured with CONFIG_PREEMPT_RT=y (real-time preemption), timer callbacks can be preempted, which was not properly handled. This caused warnings and potential issues due to improper handling of preemption in timer callbacks. The fix involved adopting preempt_disable_nested() and preempt_enable_nested() to properly manage preemption in this context.
How can this vulnerability impact me? :
The vulnerability can cause warnings and instability in the Linux kernel when running with real-time preemption enabled (CONFIG_PREEMPT_RT=y). Timer callbacks may be preempted unexpectedly, potentially leading to race conditions or inconsistent behavior in network scheduling. This could affect system reliability and performance, especially in real-time or time-sensitive environments.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability can be detected by monitoring for WARNING messages related to est_timer() in the kernel logs, especially messages referencing seqlock.h and gen_estimator.c. You can check the kernel log using commands like 'dmesg | grep est_timer' or 'journalctl -k | grep est_timer' to look for such warnings.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, update the Linux kernel to a version where the fix adopting preempt_disable_nested()/preempt_enable_nested() in est_timer() has been applied. This resolves the issue with timer callbacks being preempted when CONFIG_PREEMPT_RT=y. If updating is not immediately possible, consider disabling CONFIG_PREEMPT_RT or avoiding configurations that enable it until a patched kernel is deployed.