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NVD / CVE Program· CNA Linux

CVE-2025-38338: fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()

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: 0.18% (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 14f5549ad163be2c018abc1bb38370fff617a243, 1e93b61d3eaa14bfebcc2716ac09d43f3845d420, 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9; azl3 kernel 6.6.92.2-2 on Azure Linux 3.0 6.6.96.1-1; azl3 kernel 6.6.96.1-1 on Azure Linux 3.0 6.6.96.1-1.

Low priority for now. Upgrade to Linux Linux 14f5549ad163be2c018abc1bb38370fff617a243, 1e93b61d3eaa14bfebcc2716ac09d43f3845d420, 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9; azl3 kernel 6.6.92.2-2 on Azure Linux 3.0 6.6.96.1-1; azl3 kernel 6.6.96.1-1 on Azure Linux 3.0 6.6.96.1-1 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: fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio() Sometimes, when a file was read while it was being truncated by another NFS client, the kernel could deadlock because folio_unlock() was called twice, and the second call would XOR back the `PG_locked` flag. Most of the time (depending on the timing of the truncation), nobody notices the problem because folio_unlock() gets called three times, which flips `PG_locked` back off: 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio, nfs_return_empty_folio 2. vfs_read, nfs_read_folio, ... netfs_read_collection, netfs_unlock_abandoned_read_pages 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio, nfs_return_empty_folio The problem is that nfs_read_add_folio() is not supposed to unlock the folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is missing in nfs_return_empty_folio(). Rarely this leads to a warning in netfs_read_collection(): ------------[ cut here ]------------ R=0000031c: folio 10 is not locked WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00 [...] Workqueue: events_unbound netfs_read_collection_worker RIP: 0010:netfs_read_collection+0x7c0/0xf00 [...] Call Trace: <TASK> netfs_read_collection_worker+0x67/0x80 process_one_work+0x12e/0x2c0 worker_thread+0x295/0x3a0 Most of the time, however, processes just get stuck forever in folio_wait_bit_common(), waiting for `PG_locked` to disappear, which never happens because nobody is really holding the folio lock.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Jul 10, 2025
Updated
Nov 5, 2026
EPSS
0.1% · 8th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

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

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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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.

VendorProduct
linuxlinux kernel

Affected versions

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

  • linux linux kernel6.4 and later · before 6.6.95
  • linux linux kernel6.7 and later · before 6.12.35
  • linux linux kernel6.13 and later · before 6.15.4

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

    • 6.4affected
    • 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 and later · before 14f5549ad163be2c018abc1bb38370fff617a243affected · git
    • 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 and later · before 5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5affected · git
    • 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 and later · before 1e93b61d3eaa14bfebcc2716ac09d43f3845d420affected · git
    • 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 and later · before 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9affected · git
    • before 6.4not affected · semver
    • 6.6.95 and later · up to and including 6.6.*not affected · semver
    • 6.12.35 and later · up to and including 6.12.*not affected · semver
    • 6.15.4 and later · up to and including 6.15.*not affected · semver
    • 6.16 and laternot affected · original_commit_for_fix

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:13linuxbefore 6.12.35-16.12.35-1

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-2025-38336Jul 10, 2025 · ata: pata_via: Force PIO for ATAPI devices on VT6415/VT6330
    22Monitor
  • ← EarlierCVE-2025-38337Jul 10, 2025 · jbd2: fix data-race and null-ptr-deref in jbd2_journal_dirty_metadata()
    22Monitor
  • Later →CVE-2025-38342Jul 10, 2025 · software node: Correct a OOB check in software_node_get_reference_args()
    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 / packageFixed versionSource
Linux Linux14f5549ad163be2c018abc1bb38370fff617a243Vendor (CNA)
Linux Linux1e93b61d3eaa14bfebcc2716ac09d43f3845d420Vendor (CNA)
Linux Linux4c10fa44bc5f700e2ea21de2fbae520ba21f19d9Vendor (CNA)
Linux Linux5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5Vendor (CNA)
azl3 kernel 6.6.92.2-2 on Azure Linux 3.06.6.96.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 kernel 6.6.96.1-1 on Azure Linux 3.06.6.96.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.12.35-1 · Debian:13Package 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.

  • CVE-2026-31608288 days apartsmb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list()
    39Monitor
  • CVE-2026-31609288 days apartsmb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
    39Monitor
  • CVE-2026-43011295 days apartnet/x25: Fix potential double free of skb
    39Monitor
  • CVE-2026-43414302 days apartscsi: qla2xxx: Completely fix fcport double free
    39Monitor
  • CVE-2026-52993349 days aparttipc: fix double-free in tipc_buf_append()
    39Monitor
  • CVE-2026-63888374 days apartscsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
    39Monitor

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).

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-415 · Double Free

CVSS vector

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

nvd-primary

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

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

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

References

Show all references (3 more)

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

All records