Privileged kernel warning via callback-frame tail call
Published Sep 25, 2026 · Updated Sep 25, 2026
Improper BPF verification in Linux 6.18.2 through 6.18.52 and 6.19 allows local users with CAP_BPF to trigger a kernel warning. The verifier synthesizes an unknown R0 for a callback-frame tail call, then precision backtracking reaches the callback caller with R0 still requested and raises the callback unexpected regs warning. CAP_BPF is required, and the demonstrated consequence is a warning plus an EFAULT failure for the crafted BPF_PROG_LOAD request rather than a system crash.
Summary
What happened
Improper BPF verification in Linux 6.18.2 through 6.18.52 and 6.19 allows local users with CAP_BPF to trigger a kernel warning. The verifier synthesizes an unknown R0 for a callback-frame tail call, then precision backtracking reaches the callback caller with R0 still requested and raises the callback unexpected regs warning. CAP_BPF is required, and the demonstrated consequence is a warning plus an EFAULT failure for the crafted BPF_PROG_LOAD request rather than a system crash.
The record
- CVE
- CVE-2026-98061
- Published
- Sep 25, 2026
- Updated
- Sep 25, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Sep 25, 2026CVE publishedPublication date reported by the CVE source.
- Sep 25, 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=6.18.2 <6.18.53
- Affected versionversion=6.19
- Affected versionversion=a6c22c91b6284e4713c0cf5b20ab3c9c71b77ae8 <617c8266e49f45747f71e74177646a63f72b7025
- Affected versionversion=e3245f8990431950d20631c72236d4e8cb2dcde8 <266aa4ad0b2e82397cd9045752c9bff03d98eddd
- Affected versionversion=e3245f8990431950d20631c72236d4e8cb2dcde8 <96d31b28263c429a56e4de85bcf744a5c320b3a3
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
No sourced classifications are available.
Public exploit references
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Technologies
Your stack
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Your stack
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