8.8

CVE-2021-3491: Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass

Modified
AliasesUBUNTU-CVE-2021-3491DEBIAN-CVE-2021-3491
Published 04-06-2021Last modified 16-09-2024

Vulnerability summary

CVE-2021-3491 is a high (CVSS 8.8) Incorrect Calculation of Buffer Size vulnerability in canonical ubuntu_linux. EPSS estimates a 0.64% chance of exploitation in the next 30 days, higher than 50.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.8/10
010
High · v3.1 (NVD)
EPSS score
0.64%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 22 · Related 20
MGASA-2021-0214MGASA-2021-0215OPENSUSE-SU-2021:0843-1OPENSUSE-SU-2021:0947-1OPENSUSE-SU-2021:1975-1OPENSUSE-SU-2021:1977-1

Timeline

  1. 04-06-2021
    PublishedVulnerability first disclosed.
  2. 16-09-2024
    Last modifiedVulnerability information updated.

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).

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.64%

Chance of exploitation in the next 30 days

Percentile

51%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.64% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu16 products
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.3All versions (No fix recorded)
  • linux-azureAll versions (No fix recorded)
  • linux-azure-5.3All versions (No fix recorded)
  • linux-azure-edgeAll versions (No fix recorded)
Canonical1 product
Debian1 product
  • linux< 5.10.38-1
Linux1 product
  • linux_kernel≥ trunk, < v5.13-rc4 | ≥ linux-5.12.y, < v5.12.4 | ≥ linux-5.11.y, < v5.11.21 | ≥ linux-5.10.y, < v5.10.37 | ≥ v5.7-rc1, < 5.7* | ≥ 5.7, < 5.10.37 | ≥ 5.11, < 5.11.21 | ≥ 5.12, < 5.12.4

4 vendors · 19 products

References

10 links