Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2025-40285: smb/server: fix possible refcount leak in smb2_sess_setup()

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.41% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 379510a815cb2e64eb0a379cb62295d6ade65df0, 5.16, 6.1.159.

Low priority for now. Upgrade to Linux Linux 379510a815cb2e64eb0a379cb62295d6ade65df0, 5.16, 6.1.159 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: smb/server: fix possible refcount leak in smb2_sess_setup() Reference count of ksmbd_session will leak when session need reconnect. Fix this by adding the missing ksmbd_user_session_put().

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Dec 6, 2025
Updated
Oct 15, 2026
EPSS
0.4% · 35th percentile
CWE
—

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CNA vs NVD score

NVD
—
CNA · Linux
7.5
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.

Follow CVE-2025-40285

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

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

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.

We use this product, ask for help

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.

—

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

    • 2107ab40629aeabbec369cf34b8cf0f288c3eb1b, 6.13affected
    • 37a0e2b362b3150317fb6e2139de67b1e29ae5ff and later · before 6fc935f798d44a8eb8a5e6659198399fbf57b981affected · git
    • 450a844c045ff0895d41b05a1cbe8febd1acfcfd and later · before e671f9bb97805771380c98de944e2ceab6949188affected · git
    • a39e31e22a535d47b14656a7d6a893c7f6cf758c and later · before dcc51dfe6ff26b52cac106865a172ac982d78401affected · git
    • b95629435b84b9ecc0c765995204a4d8a913ed52 and later · before d37b2c81c83d6c0d5ca582f4fe73c672983f9e0daffected · git
    • b95629435b84b9ecc0c765995204a4d8a913ed52 and later · before 379510a815cb2e64eb0a379cb62295d6ade65df0affected · git
    • 6.1.121 and later · before 6.1.159affected · semver
    • 6.6.67 and later · before 6.6.117affected · semver
    • 6.12.6 and later · before 6.12.59affected · semver
    • 5.15.176 and later · before 5.16affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.159-16.1.159-1
Debian:13linuxbefore 6.12.63-16.12.63-1
Debian:14linuxbefore 6.17.9-16.17.9-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2025-40283Dec 6, 2025 · Bluetooth: btusb: reorder cleanup in btusb_disconnect to avoid UAF
    31Monitor
  • ← EarlierCVE-2025-40284Dec 6, 2025 · Bluetooth: MGMT: cancel mesh send timer when hdev removed
    31Monitor
  • Later →CVE-2025-40286Dec 6, 2025 · smb/server: fix possible memory leak in smb2_read()
    0Monitor

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 Linux379510a815cb2e64eb0a379cb62295d6ade65df0Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux6.1.159Vendor (CNA)
Linux Linux6.12.59Vendor (CNA)
Linux Linux6.6.117Vendor (CNA)
Linux Linux6fc935f798d44a8eb8a5e6659198399fbf57b981Vendor (CNA)
Linux Linuxd37b2c81c83d6c0d5ca582f4fe73c672983f9e0dVendor (CNA)
Linux Linuxdcc51dfe6ff26b52cac106865a172ac982d78401Vendor (CNA)
Linux Linuxe671f9bb97805771380c98de944e2ceab6949188Vendor (CNA)
debian:linux6.1.159-1 · Debian:12Package 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • 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
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

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. 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