CVE-2026-81009
In the Linux kernel, the following vulnerability has been resolved: io_uring/query: cap user size passed to copy_struct_to_user io_handle_query_entry() clamps hdr.size for the inbound copy_from_user() but keeps the original user value as usize. copy_struct_to_user() uses that usize and, when it is larger than the kernel result, clear_user()s the trailing bytes. As hdr.size is a __u32, a query can request nearly 4 GiB of zeroing, including on the error path where res_size stays 0. The interface is reachable without a ring via IORING_REGISTER_QUERY. Reject sizes larger than PAGE_SIZE, as recommended for copy_struct_* interfaces.
Affected versions
Linux kernel versions
6.18
and later are affected. Fixed in
6.18.50,
7.2.4,
7.3-rc1
and their respective stable series.
References
3 totalFrequently asked questions
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What is CVE-2026-81009?
CVE-2026-81009 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 6.18 onward and has been patched in 6.18.50, 7.2.4 and 7.3-rc1. CVE-2026-81009 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-81009?
Yes. CVE-2026-81009 has been patched. Fixed versions include 6.18.50, 7.2.4 and 7.3-rc1. If you are running Linux kernel 6.18 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-81009 actively exploited?
No. CVE-2026-81009 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.