Service interruption via zero NAPI poll weight
Published Feb 27, 2025 · Updated May 12, 2026
Improper input validation in the Linux kernel network core allows local users to interrupt service by setting dev_weight to zero. The net.core.dev_weight sysctl accepts zero, letting process_backlog clear NAPI_STATE_SCHED and be repolled until the softirq times out; enqueue_to_backlog can then retrigger scheduling and corrupt the list. Triggering the condition requires system-wide administrator access because the setting is not namespaced.
Summary
What happened
Improper input validation in the Linux kernel network core allows local users to interrupt service by setting dev_weight to zero. The net.core.dev_weight sysctl accepts zero, letting process_backlog clear NAPI_STATE_SCHED and be repolled until the softirq times out; enqueue_to_backlog can then retrigger scheduling and corrupt the list. Triggering the condition requires system-wide administrator access because the setting is not namespaced.
The record
- CVE
- CVE-2025-21806
- Published
- Feb 27, 2025
- Updated
- May 12, 2026
- Vendor
- Siemens
- Product
- SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
- Classifications
- CWE-20, T1499
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Feb 27, 2025CVE publishedPublication date reported by the CVE source.
- May 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=0 <*
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Published CVSS scores
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Attacks
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Technologies
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