CVE-2021-47259

Kernel invalid access via premature NFS client release

Published May 21, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel NFS client code allows local users to trigger an invalid kernel memory access during NFS mounts. In nfs4_init_client(), nfs_put_client() can release the last clp reference before clear_bit() dereferences that freed client object. Reaching the defect requires mounting two exports from one server through different NICs, and KASAN detects the resulting invalid access.

CVSS severity7.8
High
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel NFS client code allows local users to trigger an invalid kernel memory access during NFS mounts. In nfs4_init_client(), nfs_put_client() can release the last clp reference before clear_bit() dereferences that freed client object. Reaching the defect requires mounting two exports from one server through different NICs, and KASAN detects the resulting invalid access.

The record

CVE
CVE-2021-47259
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=4.13
  2. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <3e3c7ebbfac152d08be75c92802a64a1f6471a15
  3. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <42c10b0db064e45f5c5ae7019bbf2168ffab766c
  4. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <476bdb04c501fc64bf3b8464ffddefc8dbe01577
  5. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <72651c6579a25317a90536181d311c663d0329ab
  6. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <c3b6cf64dfe4ef96e7341508d50d6998da7062c7
  7. Affected versionversion=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <c7eab9e2d7b4e983ce280276fb920af649955897

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=4.13; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <3e3c7ebbfac152d08be75c92802a64a1f6471a15; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <42c10b0db064e45f5c5ae7019bbf2168ffab766c; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <476bdb04c501fc64bf3b8464ffddefc8dbe01577; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <72651c6579a25317a90536181d311c663d0329ab; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <c3b6cf64dfe4ef96e7341508d50d6998da7062c7; version=8dcbec6d20eb881ba368d0aebc3a8a678aebb1da <c7eab9e2d7b4e983ce280276fb920af649955897
The Linux Kernel Organization · Linux Kernelversion=4.13; version=8dcbec6d20eb <476bdb04c501

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.5CISA-ADPCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

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

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Your stack

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