NVD / CVE Program· CNA Linux

CVE-2024-26958: nfs: fix UAF in direct writes

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: 0.24% (FIRST EPSS).
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 17f46b803d4f23c66cacce81db35fef3adb8f2af, 1daf52b5ffb24870fbeda20b4967526d8f9e12ab, 3abc2d160ed8213948b147295d77d44a22c88fa3.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 17f46b803d4f23c66cacce81db35fef3adb8f2af, 1daf52b5ffb24870fbeda20b4967526d8f9e12ab, 3abc2d160ed8213948b147295d77d44a22c88fa3 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 UAF in direct writes In production we have been hitting the following warning consistently ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 17 PID: 1800359 at lib/refcount.c:28 refcount_warn_saturate+0x9c/0xe0 Workqueue: nfsiod nfs_direct_write_schedule_work [nfs] RIP: 0010:refcount_warn_saturate+0x9c/0xe0 PKRU: 55555554 Call Trace: <TASK> ? __warn+0x9f/0x130 ? refcount_warn_saturate+0x9c/0xe0 ? report_bug+0xcc/0x150 ? handle_bug+0x3d/0x70 ? exc_invalid_op+0x16/0x40 ? asm_exc_invalid_op+0x16/0x20 ? refcount_warn_saturate+0x9c/0xe0 nfs_direct_write_schedule_work+0x237/0x250 [nfs] process_one_work+0x12f/0x4a0 worker_thread+0x14e/0x3b0 ? ZSTD_getCParams_internal+0x220/0x220 kthread+0xdc/0x120 ? __btf_name_valid+0xa0/0xa0 ret_from_fork+0x1f/0x30 This is because we're completing the nfs_direct_request twice in a row. The source of this is when we have our commit requests to submit, we process them and send them off, and then in the completion path for the commit requests we have if (nfs_commit_end(cinfo.mds)) nfs_direct_write_complete(dreq); However since we're submitting asynchronous requests we sometimes have one that completes before we submit the next one, so we end up calling complete on the nfs_direct_request twice. The only other place we use nfs_generic_commit_list() is in __nfs_commit_inode, which wraps this call in a nfs_commit_begin(); nfs_commit_end(); Which is a common pattern for this style of completion handling, one that is also repeated in the direct code with get_dreq()/put_dreq() calls around where we process events as well as in the completion paths. Fix this by using the same pattern for the commit requests. Before with my 200 node rocksdb stress running this warning would pop every 10ish minutes. With my patch the stress test has been running for several hours without popping.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

BDU:2024-03636

Published: May 1, 2024
Updated: Oct 15, 2026
EPSS: 0.2% · 15th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 7.8
CNA · Linux: 7.8; agree

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.

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

Affected versions

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

debian debian linux10.0
linux linux kernel5.11 and later · before 5.15.154
linux linux kernel5.16 and later · before 6.1.84
linux linux kernelbefore 5.10.215
linux linux kernel6.7 and later · before 6.7.12
linux linux kernel6.8 and later · before 6.8.3
linux linux kernel6.2 and later · before 6.6.24

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
- 4.5affected
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 6cd3f13aaa62970b5169d990e936b2e96943bc6aaffected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 4595d90b5d2ea5fa4d318d13f59055aa4bf3e7f5affected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 80d24b308b7ee7037fc90d8ac99f6f78df0a256faffected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 3abc2d160ed8213948b147295d77d44a22c88fa3affected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before e25447c35f8745337ea8bc0c9697fcac14df8605affected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 1daf52b5ffb24870fbeda20b4967526d8f9e12abaffected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before cf54f66e1dd78990ec6b32177bca7e6ea2144a95affected · git
- af7cf057933f01dc7f33ddfb5e436ad598ed17ad and later · before 17f46b803d4f23c66cacce81db35fef3adb8f2afaffected · git
- before 4.5not 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 6.1.85-1	6.1.85-1
Debian:13	linux	before 6.7.12-1	6.7.12-1

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-2024-26953May 1, 2024 · net: esp: fix bad handling of pages from page_pool
22Monitor
← EarlierCVE-2024-26957May 1, 2024 · s390/zcrypt: fix reference counting on zcrypt card objects
31Monitor
Later →CVE-2024-26960May 1, 2024 · mm: swap: fix race between free_swap_and_cache() and swapoff()
28Monitor

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	17f46b803d4f23c66cacce81db35fef3adb8f2af	Vendor (CNA)
Linux Linux	1daf52b5ffb24870fbeda20b4967526d8f9e12ab	Vendor (CNA)
Linux Linux	3abc2d160ed8213948b147295d77d44a22c88fa3	Vendor (CNA)
Linux Linux	4595d90b5d2ea5fa4d318d13f59055aa4bf3e7f5	Vendor (CNA)
Linux Linux	6cd3f13aaa62970b5169d990e936b2e96943bc6a	Vendor (CNA)
Linux Linux	80d24b308b7ee7037fc90d8ac99f6f78df0a256f	Vendor (CNA)
Linux Linux	cf54f66e1dd78990ec6b32177bca7e6ea2144a95	Vendor (CNA)
Linux Linux	e25447c35f8745337ea8bc0c9697fcac14df8605	Vendor (CNA)
debian:linux	6.1.85-1 · Debian:12	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-24-0387 · May 2, 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-primary

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, 10:10 PM UTC

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

References

git.kernel.org/stable/c/17f46b803d4f23c66cacce81db35fef3adb8f2af

Show all references (9 more)

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

All records