# CVE-2021-4090: linux: An out-of-bounds (OOB) memory write flaw was found in the NFSD in the Linux kernel

CVE-2021-4090 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-4090, released February 18, 2022. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-4090
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0034
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 18, 2022

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-4090](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4090.md) | Feb 18, 2022 |
| Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-4090](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4090.md) | Feb 18, 2022 |
| Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-4090](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4090.md) | Feb 18, 2022 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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