Local process hang via oversized query zeroing
Published Sep 11, 2026 · Updated Sep 11, 2026
Denial of service in Linux 6.18 allows local users to hang a calling process through an oversized io_uring query response. io_handle_query_entry() clamps hdr.size only for the inbound copy, preserves the original 32-bit value as usize, and passes it to copy_struct_to_user(), which clears the excess user-space range. IORING_REGISTER_QUERY reaches this path without a ring, and an unprivileged caller can request nearly 4 GiB of zeroing, consuming kernel time and overwriting the caller's mapped memory.
Summary
What happened
Denial of service in Linux 6.18 allows local users to hang a calling process through an oversized io_uring query response. io_handle_query_entry() clamps hdr.size only for the inbound copy, preserves the original 32-bit value as usize, and passes it to copy_struct_to_user(), which clears the excess user-space range. IORING_REGISTER_QUERY reaches this path without a ring, and an unprivileged caller can request nearly 4 GiB of zeroing, consuming kernel time and overwriting the caller's mapped memory.
The record
- CVE
- CVE-2026-81009
- Published
- Sep 11, 2026
- Updated
- Sep 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 11, 2026CVE publishedPublication date reported by the CVE source.
- Sep 11, 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
- Affected versionversion=c265ae75f900cea4e415230a77b5d152377627dd <2b8ad4981ecedb14c1fdd811ab977010b23933e6
- Affected versionversion=c265ae75f900cea4e415230a77b5d152377627dd <417e02f7b6051765b91cf1289071882eebd172e0
- Affected versionversion=c265ae75f900cea4e415230a77b5d152377627dd <ba77efee1b95b4ad7559b1cdbe7cd7fa36dca95b
What conditions does exploitation require?
What is affected?
Published CVSS scores
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CVSS describes severity. EPSS estimates exploitation probability.
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.
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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