io_uring/query: cap user size passed to copy_struct_to_user (CVE-2026-81009) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-81009

io_uring/query: cap user size passed to copy_struct_to_user

Answer in brief

CVE-2026-81009 records a Unknown severity vulnerability in io_uring/query: cap user size passed to copy_struct_to_user. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 11, 2026Updated Sep 11, 2026Source checked Sep 11, 2026First seen by HOL Sep 11, 2026Material review Sep 11, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=c265ae75f900cea4e415230a77b5d152377627dd <417e02f7b6051765b91cf1289071882eebd172e0 \|\| >=c265ae75f900cea4e415230a77b5d152377627dd <2b8ad4981ecedb14c1fdd811ab977010b23933e6 \|\| >=c265ae75f900cea4e415230a77b5d152377627dd <ba77efee1b95b4ad7559b1cdbe7cd7fa36dca95b	417e02f7b6051765b91cf1289071882eebd172e0, 2b8ad4981ecedb14c1fdd811ab977010b23933e6, ba77efee1b95b4ad7559b1cdbe7cd7fa36dca95b
Linux/Linuxgeneric	6.18	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 417e02f7b6051765b91cf1289071882eebd172e0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 11, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.