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NVD / CVE Program· CNA Linux

CVE-2025-40039: ksmbd: Fix race condition in RPC handle list access

Noroxi assessment

Priority: Monitor (action score 18/100)

  • 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: 0.31% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Linux Linux 305853cce379407090a73b38c5de5ba748893aee, 5.16, 5cc679ba0f4505936124cd4179ba66bb0a4bd9f3; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.
  • Severity is disputed: the assigning authority (CNA) scores it 8.8, NVD 4.7.

Low priority for now. Upgrade to Linux Linux 305853cce379407090a73b38c5de5ba748893aee, 5.16, 5cc679ba0f4505936124cd4179ba66bb0a4bd9f3; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes 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: ksmbd: Fix race condition in RPC handle list access The 'sess->rpc_handle_list' XArray manages RPC handles within a ksmbd session. Access to this list is intended to be protected by 'sess->rpc_lock' (an rw_semaphore). However, the locking implementation was flawed, leading to potential race conditions. In ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock before calling xa_store() and xa_erase(). Since these operations modify the XArray structure, a write lock is required to ensure exclusive access and prevent data corruption from concurrent modifications. Furthermore, ksmbd_session_rpc_method() accessed the list using xa_load() without holding any lock at all. This could lead to reading inconsistent data or a potential use-after-free if an entry is concurrently removed and the pointer is dereferenced. Fix these issues by: 1. Using down_write() and up_write() in ksmbd_session_rpc_open() to ensure exclusive access during XArray modification, and ensuring the lock is correctly released on error paths. 2. Adding down_read() and up_read() in ksmbd_session_rpc_method() to safely protect the lookup.

MediumCVSS 4.7 · v3.1—No exploit Fix available
Published
Oct 28, 2025
Updated
Oct 19, 2026
EPSS
0.3% · 24th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CNA vs NVD score

NVD
4.7
CNA · Linux
8.8
4.1 point gap

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

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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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • 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 kernel5.15.145 and later · before 5.16
  • linux linux kernel6.1.71 and later · before 6.2
  • linux linux kernel6.3 and later · before 6.6.123
  • linux linux kernel6.7 and later · before 6.12.53
  • linux linux kernel6.13 and later · before 6.17.3

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

    • 1f485b54d04a920723984062c912174330a05178, 052b41ef2abe274f068e892aee81406f11bd1f3a, 6.3affected
    • a4348710a7267705b75692dc1a000920481d1d92 and later · before 69674b029002b1d90b655f014bdf64f404efa54daffected · git
    • b685757c7b08d5073046fb379be965fd6c06aafc and later · before 6b615a8fb3af0baf8126cde3d4fee97d57222ffcaffected · git
    • b685757c7b08d5073046fb379be965fd6c06aafc and later · before 5cc679ba0f4505936124cd4179ba66bb0a4bd9f3affected · git
    • b685757c7b08d5073046fb379be965fd6c06aafc and later · before 6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1affected · git
    • b685757c7b08d5073046fb379be965fd6c06aafc and later · before 305853cce379407090a73b38c5de5ba748893aeeaffected · git
    • 5.15.145 and later · before 5.16affected · semver
    • before 6.3not affected · semver
    • 6.6.123 and later · up to and including 6.6.*not affected · semver
    • 6.12.53 and later · up to and including 6.12.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.162-16.1.162-1
Debian:13linuxbefore 6.12.57-16.12.57-1
Debian:14linuxbefore 6.17.6-16.17.6-1
openSUSE:Tumbleweedkernel-sourcebefore 6.17.7-1.16.17.7-1.1

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-2025-39967Oct 15, 2025 · fbcon: fix integer overflow in fbcon_do_set_font
    31Monitor
  • ← EarlierCVE-2025-40005Oct 20, 2025 · spi: cadence-quadspi: Implement refcount to handle unbind during busy
    22Monitor
  • Later →CVE-2025-40040Oct 28, 2025 · mm/ksm: fix flag-dropping behavior in ksm_madvise
    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 / packageFixed versionSource
Linux Linux305853cce379407090a73b38c5de5ba748893aeeVendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux5cc679ba0f4505936124cd4179ba66bb0a4bd9f3Vendor (CNA)
Linux Linux69674b029002b1d90b655f014bdf64f404efa54dVendor (CNA)
Linux Linux6b615a8fb3af0baf8126cde3d4fee97d57222ffcVendor (CNA)
Linux Linux6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1Vendor (CNA)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.1.162-1 · Debian:12Package registry (OSV)
opensuse:kernel-source6.17.7-1.1 · openSUSE:TumbleweedPackage 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).

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.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

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

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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

References

Show all references (4 more)

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

All records