CVE-2026-80811
Received Received - Intake

Memory Leak in Linux Kernel io_uring/cmd

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: io_uring/cmd: fix iovec leak when the async cmd is not recycled An io_async_cmd carries an iovec array in ->vec.iovec, allocated when the vec has to grow and kept across recycling through ctx->cmd_cache. On two paths nothing frees it and io_clean_op()'s kfree(req->async_data) drops the io_async_cmd without it. io_req_uring_cleanup() clears the async data flags only when io_alloc_cache_put() succeeds, and the cache holds IO_ALLOC_CACHE_MAX == 128 entries, so once it is full the put fails and the vec is left behind. An NVMe passthrough workload gets there without doing anything unusual: nvme_uring_cmd_io() returns -EIOCBQUEUED, so the io_async_cmd stays attached for the lifetime of the command and the live object count tracks the queue depth. Above 128 the puts start failing. ->cleanup is the last chance to free an inherited vec, since io_req_uring_cleanup() returns early for an io-wq issued command and is not called at all for one completed without ever being issued. But io_clean_op() calls ->cleanup only if REQ_F_NEED_CLEANUP is set, and for uring_cmd that happens only where the vec has to grow, so a command reusing a large enough cached vec never sets it. io_rw_alloc_async() and io_msg_alloc_async() flag an inherited vec for exactly this reason; io_uring_cmd_prep() does not. Flag an inherited vec in io_uring_cmd_prep(), and free the vec when the cache put fails, as io_req_rw_cleanup() does. The leak is invisible under KASAN, where io_alloc_cache_vec_kasan() frees the vec unconditionally.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-04
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80811
EUVD
EUVD-2026-71246

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a memory leak in the io_uring subsystem. When an async command uses an iovec array that grows, the array is not properly freed in certain code paths. Specifically, the iovec array remains allocated when the async command is not recycled, leading to memory leaks. The issue occurs because cleanup functions fail to free the iovec array under specific conditions, such as when the command cache is full or when certain flags are not set.

Detection Guidance

This vulnerability is specific to the Linux kernel's io_uring subsystem and may not have direct network detection methods. Monitor kernel logs for io_uring-related errors or memory leaks. Check for elevated memory usage in processes using io_uring. Commands like 'dmesg | grep io_uring' or 'journalctl -k | grep io_uring' may help identify issues.

Impact Analysis

This vulnerability can lead to memory exhaustion over time, as the leaked iovec arrays accumulate. For systems running workloads that frequently use io_uring, such as NVMe passthrough operations, this could cause performance degradation or system instability due to increased memory usage. Users may experience slower system performance or crashes if the memory leak becomes severe.

Mitigation Strategies

Update the Linux kernel to a patched version that includes the fix for CVE-2026-80811. If immediate patching is not possible, consider disabling io_uring functionality temporarily by setting 'io_uring=0' in kernel parameters or restricting its use via systemd settings.

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