CVE-2021-3491

highpriority · track · 35EPSS 0.006 · 51 %ileEURUUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
0.64% (51st) EPSS
CVSS 7.2 · high
Is it mine?
25 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

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).

01

cvss

Technical severity, 0–10. One row per scoring source.

8.8
010

base score 0–10 · higher = more severe · hover a vector to decode

v2.07.2highAV:L/AC:L/Au:N/C:C/I:C/A:Cprimary · NVD / NIST USexploitability 3.9 · impact 10
v3.18.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 2 · impact 6
v3.18.8highAV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU
v3.17.8highCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · ENISA EU
v3.17.8highCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · security@ubuntu.comexploitability 1.1 · impact 6
v3.18.1highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)
02

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-787USprimaryCWE-131USCWE-131USCWE-787US
03

affected products (25)

Products and version ranges known to be affected.

showing 20 of 25
04

advisories (1)

Vendor and ecosystem advisories describing this.

  • PUB-A-1908771002021-09-01vendor · osvUS

    In io_add_buffers of io_uring.c, there is a possible out of bounds write due to an incorrect bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.

05

also known as (5)

Other names and identifiers for this entity.

06

sources

Which sources assert this record, and when.

cnnvdenisa_euvdfstec_bduosvnvdNVDCVE.orgMITRE
published 2021-06-04modified 2026-06-17
08

references (27)

External citations — patches, advisories, analysis.

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