What is CVE-2021-4090?

CVE-2021-4090 is a High severity Linux kernel vulnerability with a CVSS score of 7.1 out of 10, classified as a Out-of-bounds Write flaw (CWE-787), affecting Linux kernel versions from 5.11 onward and patched in 5.15.5. CVE-2021-4090 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2021-4090?

CVE-2021-4090 has a CVSS score of 7.1 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

Is there a patch available for CVE-2021-4090?

Yes, CVE-2021-4090 has been patched. Fixed versions include 5.15.5. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2021-4090 actively exploited?

CVE-2021-4090 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is Out-of-bounds Write (CWE-787)?

The product writes data past the end or before the beginning of the intended buffer. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/787.html

CVE-2021-4090

High

An out-of-bounds (OOB) memory write flaw was found in the NFSD in the Linux kernel. Missing sanity may lead to a write beyond bmval[bmlen-1] in nfsd4_decode_bitmap4 in fs/nfsd/nfs4xdr.c. In this flaw, a local attacker with user privilege may gain access to out-of-bounds memory, leading to a system integrity and confidentiality threat.

Package Linux Kernel

Published 2022-02-18

Last modified 2026-08-25

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

7.1

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Vector string

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

Weakness type

CWE-787

CVE-2021-4090 is a Out-of-bounds Write vulnerability

What is Out-of-bounds Write?

The product writes data past the end or before the beginning of the intended buffer. Learn more on MITRE CWE

Affected versions

Linux kernel versions 5.11 and later are affected. Fixed in 5.15.5 and their respective stable series.

Affected from

≥ 5.11

Fixed in

✓ 5.15.5 5.15.x

References

5 total

Red Hat
https://bugzilla.redhat.com/show_bug.cgi?id=2025101

Issue Tracking Patch Third Party Advisory
Kernel Git
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c0019b7db1d7ac62c711cda6b357a659d46428fe
Kernel.org
https://lore.kernel.org/linux-nfs/163692036074.16710.5678362976688977923.stgit%40klimt.1015granger.net/
Security
https://security.netapp.com/advisory/ntap-20220318-0010/

Third Party Advisory
Cert-Portal
https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Details

CVE ID CVE-2021-4090

Severity High

CVSS score 7.1 / 10

CVSS version 3.1

Published 2022-02-18

Modified 2026-08-25

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2021-4090?

CVE-2021-4090 is a High severity Linux kernel vulnerability with a CVSS score of 7.1 out of 10 , classified as an Out-of-bounds Write flaw (CWE-787) . It affects Linux kernel versions from 5.11 onward and has been patched in 5.15.5. CVE-2021-4090 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2021-4090?

CVE-2021-4090 has a CVSS score of 7.1 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
Is there a patch available for CVE-2021-4090?

Yes. CVE-2021-4090 has been patched. Fixed versions include 5.15.5. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2021-4090 actively exploited?

No. CVE-2021-4090 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.