CVE-2021-3491

HighCVSS 8.8/10Last modified Jun 17, 2026

Description

The io_uring subsystem in the Linux kernel allowed the MAX_RW_COUNT limit to be bypassed in the PROVIDE_BUFFERS operation, which led to negative values being usedin mem_rw when reading /proc/<PID>/mem. This could be used to create a heap overflow leading to arbitrary code execution in the kernel. It was addressed via commit d1f82808877b ("io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers") (v5.13-rc1) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced in ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS") (v5.7-rc1).

Metrics

CVSS 3.1 8.8/10CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Weakness enumeration

CWE-131CWE-787

Affected software

No affected versions have been published.

Timeline

Published
Jun 4, 2021
Last modified
Jun 17, 2026
NVD status
Modified

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CVE-2021-3491: High severity, CVSS 8.8 | Vulnix