CVE-2021-3491 - CVE House

Back to Database

Status published High CVE-2021-3491

Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass

7.8 CVSS

Vulnerability 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).

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

THREAT MONITOR

Am I Vulnerable?

Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2021-3491

Check My Exposure

Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

Billy Jheng Bing-Jhong (@st424204) of STAR Labs working with Trend Micro's Zero Day Initiative

References

More from Linux

View All →

drm/vkms: Convert to DRM's vblank timer

drm/panthor: Recover from panthor_gpu_flush_caches() failures

PCI: endpoint: Add missing NULL check for alloc_workqueue()

fs/ntfs3: fix ntfs_mount_options leak in ntfs_fill_super()

fs/ntfs3: Initialize new folios before use

Affected Vendor

Linux

View all reports →

Affected Software

Linux kernel

Vulnerable Versions:

trunk, linux-5.12.y, linux-5.11.y, linux-5.10.y, v5.7-rc1

Timeline

Official Publish: June 4th, 2021

Last Modified: September 16th, 2024

Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Weaknesses (CWE)

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.