🛡️ CVE-2021-4090 on Debian — linux

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

Description

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.

Distribution advisory

This page covers CVE-2021-4090 as tracked by Debian, for the package linux. The fix is available in version 5.15.5-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability none.

Affected software

DEBIAN-CVE-2021-4090 is recorded against 1 package.

linux (fixed in 5.15.5-1)

Timeline and source

Published on 18 February 2022 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2021-4090 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Ubuntu

Details

Severity Unknown

CVSS Score N/A

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

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2022-02-18

Updated 2026-08-20

Modified 2026-08-04

Fix URL N/A

Affected Packages

Software	From version	Fixed in
linux	—	5.15.5-1

References

ADVISORY https://security-tracker.debian.org/tracker/CVE-2021-4090

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