NVD / CVE Program· CNA Linux

CVE-2021-47259: NFS: Fix use-after-free in nfs4_init_client()

Noroxi assessment

Priority: Monitor (action score 31/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.71% (FIRST EPSS); higher than 53.6% of all records.
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 3e3c7ebbfac152d08be75c92802a64a1f6471a15, 42c10b0db064e45f5c5ae7019bbf2168ffab766c, 476bdb04c501fc64bf3b8464ffddefc8dbe01577.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 3e3c7ebbfac152d08be75c92802a64a1f6471a15, 42c10b0db064e45f5c5ae7019bbf2168ffab766c, 476bdb04c501fc64bf3b8464ffddefc8dbe01577 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: NFS: Fix use-after-free in nfs4_init_client() KASAN reports a use-after-free when attempting to mount two different exports through two different NICs that belong to the same server. Olga was able to hit this with kernels starting somewhere between 5.7 and 5.10, but I traced the patch that introduced the clear_bit() call to 4.13. So something must have changed in the refcounting of the clp pointer to make this call to nfs_put_client() the very last one.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

Published: May 21, 2024
Updated: Aug 5, 2026
EPSS: 0.7% · 53th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.7%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Linux: 7.8; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

ProductVersion

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel4.13 and later · before 4.14.237
linux linux kernel4.15 and later · before 4.19.195
linux linux kernel4.20 and later · before 5.4.126
linux linux kernel5.5 and later · before 5.10.44
linux linux kernel5.11 and later · before 5.12.11
linux linux kernel5.13

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

Linux Linux
- 4.13affected
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before c7eab9e2d7b4e983ce280276fb920af649955897affected · git
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before 42c10b0db064e45f5c5ae7019bbf2168ffab766caffected · git
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before 3e3c7ebbfac152d08be75c92802a64a1f6471a15affected · git
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before c3b6cf64dfe4ef96e7341508d50d6998da7062c7affected · git
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before 72651c6579a25317a90536181d311c663d0329abaffected · git
- 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da and later · before 476bdb04c501fc64bf3b8464ffddefc8dbe01577affected · git
- before 4.13not affected · semver
- 4.14.237 and later · up to and including 4.14.*not affected · semver
- 4.19.195 and later · up to and including 4.19.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 5.10.46-1	5.10.46-1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-default-base	before 5.3.18-150200.24.194.1.150200.9.99.1	5.3.18-150200.24.194.1.150200.9.99.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-docs	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-obs-build	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-preempt	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-source	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-syms	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise Live Patching 15 SP2	kernel-default	before 5.3.18-150200.24.194.1	5.3.18-150200.24.194.1
SUSE:Linux Enterprise Live Patching 15 SP2	kernel-livepatch-SLE15-SP2_Update_49	before 1-150200.5.3.1	1-150200.5.3.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
90Now
CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2021-47257May 21, 2024 · net: ieee802154: fix null deref in parse dev addr
22Monitor
← EarlierCVE-2021-47258May 21, 2024 · scsi: core: Fix error handling of scsi_host_alloc()
22Monitor
Later →CVE-2021-47260May 21, 2024 · NFS: Fix a potential NULL dereference in nfs_get_client()
22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Linux Linux	3e3c7ebbfac152d08be75c92802a64a1f6471a15	Vendor (CNA)
Linux Linux	42c10b0db064e45f5c5ae7019bbf2168ffab766c	Vendor (CNA)
Linux Linux	476bdb04c501fc64bf3b8464ffddefc8dbe01577	Vendor (CNA)
Linux Linux	72651c6579a25317a90536181d311c663d0329ab	Vendor (CNA)
Linux Linux	c3b6cf64dfe4ef96e7341508d50d6998da7062c7	Vendor (CNA)
Linux Linux	c7eab9e2d7b4e983ce280276fb920af649955897	Vendor (CNA)
debian:linux	5.10.46-1 · Debian:12	Package registry (OSV)
suse:kernel-default	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise Live Patching 15 SP2	Package registry (OSV)
suse:kernel-default-base	5.3.18-150200.24.194.1.150200.9.99.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)
suse:kernel-docs	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)
suse:kernel-livepatch-SLE15-SP2_Update_49	1-150200.5.3.1 · SUSE:Linux Enterprise Live Patching 15 SP2	Package registry (OSV)
suse:kernel-obs-build	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)
suse:kernel-preempt	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)
suse:kernel-source	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)
suse:kernel-syms	5.3.18-150200.24.194.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-24-0519 · May 22, 2024(Linux Kernel Güncellemesi)

All national notices →

Technical details

Attack conditions

Someone with local access to the system can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

For records you follow, these changes also arrive as notifications. →

References

git.kernel.org/stable/c/3e3c7ebbfac152d08be75c92802a64a1f6471a15

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records