Local privilege escalation via ETS negative index
Published Feb 10, 2025 · Updated Aug 5, 2026
Improper array-index validation in Linux kernel 5.6 and later allows local users to elevate privileges through ETS qdisc changes. ets_class_from_arg subtracts one from a zero class identifier, selecting ets_class[-1], and ets_class_change then writes an attacker-chosen quantum through that invalid pointer. The path requires CAP_NET_ADMIN, obtainable in an enabled unprivileged user namespace, and can corrupt kernel memory, disclose adjacent data, or crash the host.
Summary
What happened
Improper array-index validation in Linux kernel 5.6 and later allows local users to elevate privileges through ETS qdisc changes. ets_class_from_arg subtracts one from a zero class identifier, selecting ets_class[-1], and ets_class_change then writes an attacker-chosen quantum through that invalid pointer. The path requires CAP_NET_ADMIN, obtainable in an enabled unprivileged user namespace, and can corrupt kernel memory, disclose adjacent data, or crash the host.
The record
- CVE
- CVE-2025-21692
- Published
- Feb 10, 2025
- Updated
- Aug 5, 2026
- Vendor
- Siemens
- Product
- SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family
- Classifications
- CWE-129, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 10, 2025CVE publishedPublication date reported by the CVE source.
- Aug 5, 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=0 <V3.2
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What is affected?
Published CVSS scores
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Attacks
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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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