CVE-2021-3491
HIGHDescription
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).
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Exploit Intelligence
Moderate risk: more likely to be exploited than 47% of all known CVEs.
References
Related Vulnerabilities
Other CWE-131 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-36824 | High | 7.4 | 77% | - | Fix |
| CVE-2020-8450 | High | 7.3 | 72% | - | Fix |
| CVE-2020-6113 | High | 7.8 | 69% | - | - |
| CVE-2026-42945 | Critical | 8.1 | 66% | - | Fix |
| CVE-2020-6116 | High | 7.8 | 28% | - | - |
| CVE-2005-3120 | Critical | 9.8 | 23% | - | Fix |
Common questions
How do I fix CVE-2021-3491?
Published advisories record a fix for 14 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-3491 being actively exploited?
Not that we know of. CVE-2021-3491 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.63% is the estimated probability that it will be exploited in the next 30 days. That is higher than 47% of all scored CVEs.
How severe is CVE-2021-3491?
CVE-2021-3491 has a CVSS v3 base score of 7.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-3491 affect?
Published advisories record a fix for linux (Debian), linux-hwe-5.8 (Ubuntu), linux-image-5.10.0-1026-oem (Ubuntu), linux-image-5.8.0-53-generic (Ubuntu), and 10 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.