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NVD / CVE Program· CNA Linux

CVE-2025-40090: ksmbd: fix recursive locking in RPC handle list access

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.28% (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 1891abe832cbf5a11039e088766131d0f1642d02, 3412fbd81b46b9cfae013817b61d4bbd27e09e36, 4602b8cee1481dbb896182e5cb1e8cf12910e9e7.
  • Severity is disputed: the assigning authority (CNA) scores it 7.5, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 1891abe832cbf5a11039e088766131d0f1642d02, 3412fbd81b46b9cfae013817b61d4bbd27e09e36, 4602b8cee1481dbb896182e5cb1e8cf12910e9e7 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 recursive locking in RPC handle list access Since commit 305853cce3794 ("ksmbd: Fix race condition in RPC handle list access"), ksmbd_session_rpc_method() attempts to lock sess->rpc_lock. This causes hung connections / tasks when a client attempts to open a named pipe. Using Samba's rpcclient tool: $ rpcclient //192.168.1.254 -U user%password $ rpcclient $> srvinfo <connection hung here> Kernel side: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/0:0 state:D stack:0 pid:5021 tgid:5021 ppid:2 flags:0x00200000 Workqueue: ksmbd-io handle_ksmbd_work Call trace: __schedule from schedule+0x3c/0x58 schedule from schedule_preempt_disabled+0xc/0x10 schedule_preempt_disabled from rwsem_down_read_slowpath+0x1b0/0x1d8 rwsem_down_read_slowpath from down_read+0x28/0x30 down_read from ksmbd_session_rpc_method+0x18/0x3c ksmbd_session_rpc_method from ksmbd_rpc_open+0x34/0x68 ksmbd_rpc_open from ksmbd_session_rpc_open+0x194/0x228 ksmbd_session_rpc_open from create_smb2_pipe+0x8c/0x2c8 create_smb2_pipe from smb2_open+0x10c/0x27ac smb2_open from handle_ksmbd_work+0x238/0x3dc handle_ksmbd_work from process_scheduled_works+0x160/0x25c process_scheduled_works from worker_thread+0x16c/0x1e8 worker_thread from kthread+0xa8/0xb8 kthread from ret_from_fork+0x14/0x38 Exception stack(0x8529ffb0 to 0x8529fff8) The task deadlocks because the lock is already held: ksmbd_session_rpc_open down_write(&sess->rpc_lock) ksmbd_rpc_open ksmbd_session_rpc_method down_read(&sess->rpc_lock) <-- deadlock Adjust ksmbd_session_rpc_method() callers to take the lock when necessary.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Oct 30, 2025
Updated
Oct 19, 2026
EPSS
0.2% · 20th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CNA vs NVD score

NVD
5.5
CNA · Linux
7.5
2.0 point gap

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

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  • 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 kernel6.12.53 and later · before 6.12.55
  • linux linux kernel6.17.3 and later · before 6.17.5
  • linux linux kernel6.18

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

    • 69674b029002b1d90b655f014bdf64f404efa54d and later · before 5493571f4351f74e11db9943e98a07c56467cf7eaffected · git
    • 6b615a8fb3af0baf8126cde3d4fee97d57222ffc and later · before 1891abe832cbf5a11039e088766131d0f1642d02affected · git
    • 5cc679ba0f4505936124cd4179ba66bb0a4bd9f3 and later · before 4602b8cee1481dbb896182e5cb1e8cf12910e9e7affected · git
    • 6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1 and later · before 3412fbd81b46b9cfae013817b61d4bbd27e09e36affected · git
    • 305853cce379407090a73b38c5de5ba748893aee and later · before 88f170814fea74911ceab798a43cbd7c5599bed4affected · git
    • 6.12.53 and later · before 6.12.55affected · semver
    • 6.17.3 and later · before 6.17.5affected · semver

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-2025-40040Oct 28, 2025 · mm/ksm: fix flag-dropping behavior in ksm_madvise
    22Monitor
  • ← EarlierCVE-2025-40082Oct 28, 2025 · hfsplus: fix slab-out-of-bounds read in hfsplus_uni2asc()
    28Monitor
  • Later →CVE-2025-40149Nov 12, 2025 · tls: Use __sk_dst_get() and dst_dev_rcu() in get_netdev_for_sock().
    31Monitor

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 Linux1891abe832cbf5a11039e088766131d0f1642d02Vendor (CNA)
Linux Linux3412fbd81b46b9cfae013817b61d4bbd27e09e36Vendor (CNA)
Linux Linux4602b8cee1481dbb896182e5cb1e8cf12910e9e7Vendor (CNA)
Linux Linux5493571f4351f74e11db9943e98a07c56467cf7eVendor (CNA)
Linux Linux6.12.55Vendor (CNA)
Linux Linux6.17.5Vendor (CNA)
Linux Linux88f170814fea74911ceab798a43cbd7c5599bed4Vendor (CNA)

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-2026-43185188 days apartksmbd: fix signededness bug in smb_direct_prepare_negotiation()
    39Monitor
  • CVE-2025-3845997 days apartatm: clip: Fix infinite recursive call of clip_push().
    31Monitor
  • CVE-2026-53202238 days apartaccel/ivpu: Fix signed integer truncation in IPC receive
    31Monitor
  • CVE-2026-53267238 days apartnetfilter: nft_ct: bail out on template ct in get eval
    31Monitor
  • CVE-2024-35886529 days apartipv6: Fix infinite recursion in fib6_dump_done().
    31Monitor
  • CVE-2026-53395262 days apartnfsd: fix dead ACL conflict guard in nfsd4_create
    30Monitor

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

Weakness class (CWE)

CWE-674 · Uncontrolled Recursion

CVSS vector

CVSS:3.1/AV:L/AC:L/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