CVE-2025-22074Network attack vector

Service hang via unbalanced oplock reference count

Published Apr 16, 2025 · Updated Aug 5, 2026

Reference-count underflow in ksmbd allows remote authenticated users to hang the Linux SMB service through crafted oplock activity. handle_ksmbd_work decrements a connection's r_count even when the oplock-break path did not increment it, so teardown can wait forever for zero. A valid low-privileged SMB share session and two attacker-controlled connections are required; repeated triggers can exhaust connection resources.

CVSS severity8.8
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reference-count underflow in ksmbd allows remote authenticated users to hang the Linux SMB service through crafted oplock activity. handle_ksmbd_work decrements a connection's r_count even when the oplock-break path did not increment it, so teardown can wait forever for zero. A valid low-privileged SMB share session and two attacker-controlled connections are required; repeated triggers can exhaust connection resources.

The record

CVE
CVE-2025-22074
Published
Apr 16, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 16, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=09aeab68033161cb54f194da93e51a11aee6144b <4790bcb269e5d6d88200a67c54ae6d627332a3be
  2. Affected versionversion=3aa660c059240e0c795217182cf7df32909dd917 <c2ec33d46b4d1c8085dab5d02e00b21f4f0fb8a9
  3. Affected versionversion=3aa660c059240e0c795217182cf7df32909dd917 <ddb7ea36ba7129c2ed107e2186591128618864e1
  4. Affected versionversion=6.12.20 <6.12.23
  5. Affected versionversion=6.13.8 <6.13.11
  6. Affected versionversion=6.14
  7. Affected versionversion=6.6.84 <6.6.87
  8. Affected versionversion=a4261bbc33fbf99b99c80aa3a2c5097611802980 <457db486203c90e10c3efc87fd45cc7000b1cd36
  9. Affected versionversion=f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa <20378cf48359f39dee0ef9b61470ebe77bd49c0d

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=09aeab68033161cb54f194da93e51a11aee6144b <4790bcb269e5d6d88200a67c54ae6d627332a3be; version=3aa660c059240e0c795217182cf7df32909dd917 <c2ec33d46b4d1c8085dab5d02e00b21f4f0fb8a9; version=3aa660c059240e0c795217182cf7df32909dd917 <ddb7ea36ba7129c2ed107e2186591128618864e1; version=6.12.20 <6.12.23; version=6.13.8 <6.13.11; version=6.14; version=6.6.84 <6.6.87; version=a4261bbc33fbf99b99c80aa3a2c5097611802980 <457db486203c90e10c3efc87fd45cc7000b1cd36; version=f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa <20378cf48359f39dee0ef9b61470ebe77bd49c0d

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
8.8LinuxCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5Amazon LinuxCVSS: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

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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
Privilegesauthenticated
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

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Your stack

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