CVE-2021-46952

Data read and service interrupt via retrans shift

Published Feb 27, 2024 · Updated May 11, 2026

Out-of-bounds read in affected Linux kernels allows local users to read kernel data or interrupt service through a crafted UDP NFS mount. The xprt_calc_majortimeo() function shifts a 64-bit value by the unvalidated retrans mount option when UDP transport is selected, accepting values of 64 or greater. Reachability requires local access and the ability to submit a UDP NFS mount request; the record does not specify whether interruption is a hang, crash, or reboot.

CVSS severity7.1
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in affected Linux kernels allows local users to read kernel data or interrupt service through a crafted UDP NFS mount. The xprt_calc_majortimeo() function shifts a 64-bit value by the unvalidated retrans mount option when UDP transport is selected, accepting values of 64 or greater. Reachability requires local access and the ability to submit a UDP NFS mount request; the record does not specify whether interruption is a hang, crash, or reboot.

The record

CVE
CVE-2021-46952
Published
Feb 27, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.6
  2. Affected versionversion=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <2f3380121d49e829fb73ba86240c181bc32ad897
  3. Affected versionversion=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <3d0163821c035040a46d816a42c0780f0f0a30a8
  4. Affected versionversion=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2
  5. Affected versionversion=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <c09f11ef35955785f92369e25819bf0629df2e59

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.6; version=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <2f3380121d49e829fb73ba86240c181bc32ad897; version=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <3d0163821c035040a46d816a42c0780f0f0a30a8; version=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2; version=9954bf92c0cddd50a2a470be302e1c1ffdf21d42 <c09f11ef35955785f92369e25819bf0629df2e59

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
7.1UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo