CVE-2025-39720Network attack vector

Kernel memory exhaustion via missed reference decrement

Published Sep 5, 2025 · Updated Sep 5, 2025

Resource exhaustion in Linux ksmbd allows remote attackers to exhaust kernel memory through SMB2 file and connection operations. The smb_lazy_parent_lease_break_close path returns when ksmbd_conn_releasing(opinfo->conn) is true without dropping the oplock_info reference, leaving its connection, transport, socket, and lease allocations unreleased. Guest-mapped shares require no credentials; otherwise an ordinary SMB account can repeat leased open and disconnect sequences until the kernel runs out of memory.

CVSS severity7.5
High
EPSS probability0.28%
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 ksmbd allows remote attackers to exhaust kernel memory through SMB2 file and connection operations. The smb_lazy_parent_lease_break_close path returns when ksmbd_conn_releasing(opinfo->conn) is true without dropping the oplock_info reference, leaving its connection, transport, socket, and lease allocations unreleased. Guest-mapped shares require no credentials; otherwise an ordinary SMB account can repeat leased open and disconnect sequences until the kernel runs out of memory.

The record

CVE
CVE-2025-39720
Published
Sep 5, 2025
Updated
Sep 5, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 5, 2025Record 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <36e010bb865fbaa1202fe9bcce3fd486d6db7606
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <89bb430f621124af39bb31763c4a8b504c9651e2
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9a7abce6e8c0e2145b346a6d4abf0d9655e9b0e8
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a1d2bab4d53368a526c97aba92671dd71814f95a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <36e010bb865fbaa1202fe9bcce3fd486d6db7606; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <89bb430f621124af39bb31763c4a8b504c9651e2; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9a7abce6e8c0e2145b346a6d4abf0d9655e9b0e8; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a1d2bab4d53368a526c97aba92671dd71814f95a

Published CVSS scores

7.5Linux Kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.001OS Exhaustion Flood

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