CVE-2025-40285Network attack vector

Unauthenticated host hang via session reference leak

Published Dec 6, 2025 · Updated Aug 5, 2026

Resource exhaustion in Linux kernel ksmbd allows remote attackers to hang hosts by sending crafted SMB2 session traffic. In smb2_sess_setup(), the reconnect path acquires a ksmbd_session reference but omits ksmbd_user_session_put(), permanently pinning the session and its open file references. Unauthenticated attackers can race SESSION_SETUP with LOGOFF on their own TCP/445 connections; repeated wins exhaust kernel memory and handles, causing an out-of-memory condition or system hang.

CVSS severity7.5
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Resource exhaustion in Linux kernel ksmbd allows remote attackers to hang hosts by sending crafted SMB2 session traffic. In smb2_sess_setup(), the reconnect path acquires a ksmbd_session reference but omits ksmbd_user_session_put(), permanently pinning the session and its open file references. Unauthenticated attackers can race SESSION_SETUP with LOGOFF on their own TCP/445 connections; repeated wins exhaust kernel memory and handles, causing an out-of-memory condition or system hang.

The record

CVE
CVE-2025-40285
Published
Dec 6, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 6, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2107ab40629aeabbec369cf34b8cf0f288c3eb1b
  2. Affected versionversion=37a0e2b362b3150317fb6e2139de67b1e29ae5ff <6fc935f798d44a8eb8a5e6659198399fbf57b981
  3. Affected versionversion=450a844c045ff0895d41b05a1cbe8febd1acfcfd <e671f9bb97805771380c98de944e2ceab6949188
  4. Affected versionversion=5.15.176 <5.16
  5. Affected versionversion=6.1.121 <6.1.159
  6. Affected versionversion=6.12.6 <6.12.59
  7. Affected versionversion=6.13
  8. Affected versionversion=6.6.67 <6.6.117
  9. Affected versionversion=a39e31e22a535d47b14656a7d6a893c7f6cf758c <dcc51dfe6ff26b52cac106865a172ac982d78401
  10. Affected versionversion=b95629435b84b9ecc0c765995204a4d8a913ed52 <379510a815cb2e64eb0a379cb62295d6ade65df0
  11. Affected versionversion=b95629435b84b9ecc0c765995204a4d8a913ed52 <d37b2c81c83d6c0d5ca582f4fe73c672983f9e0d

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2107ab40629aeabbec369cf34b8cf0f288c3eb1b; version=37a0e2b362b3150317fb6e2139de67b1e29ae5ff <6fc935f798d44a8eb8a5e6659198399fbf57b981; version=450a844c045ff0895d41b05a1cbe8febd1acfcfd <e671f9bb97805771380c98de944e2ceab6949188; version=5.15.176 <5.16; version=6.1.121 <6.1.159; version=6.12.6 <6.12.59; version=6.13; version=6.6.67 <6.6.117; version=a39e31e22a535d47b14656a7d6a893c7f6cf758c <dcc51dfe6ff26b52cac106865a172ac982d78401; version=b95629435b84b9ecc0c765995204a4d8a913ed52 <379510a815cb2e64eb0a379cb62295d6ade65df0; version=b95629435b84b9ecc0c765995204a4d8a913ed52 <d37b2c81c83d6c0d5ca582f4fe73c672983f9e0d

Published CVSS scores

7.5LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo