System crash via uninitialized connection-count fields
Published Apr 1, 2025 · Updated Sep 8, 2026
Use of uninitialized data in Linux kernel nf_conncount allows local users to crash affected systems through connection counting. insert_tree() allocates nf_conncount_tuple without initializing cpu and jiffies32, and find_or_evict() later reads those indeterminate fields while evaluating connlimit traffic. Exploitation requires local low-privileged access and a path through the connlimit logic; affected Siemens MFP controllers embed the vulnerable GNU/Linux subsystem.
Summary
What happened
Use of uninitialized data in Linux kernel nf_conncount allows local users to crash affected systems through connection counting. insert_tree() allocates nf_conncount_tuple without initializing cpu and jiffies32, and find_or_evict() later reads those indeterminate fields while evaluating connlimit traffic. Exploitation requires local low-privileged access and a path through the connlimit logic; affected Siemens MFP controllers embed the vulnerable GNU/Linux subsystem.
The record
- CVE
- CVE-2025-21959
- Published
- Apr 1, 2025
- Updated
- Sep 8, 2026
- Vendor
- Siemens
- Product
- SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
- Classifications
- CWE-908, T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 1, 2025CVE publishedPublication date reported by the CVE source.
- Sep 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=V3.1.6 <*
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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