CVE-2025-21725Network attack vector

CIFS service interruption via zero link speed

Published Feb 27, 2025 · Updated Aug 5, 2026

Divide-by-zero in the Linux CIFS client allows remote attackers controlling an SMB server to interrupt CIFS service through a zero link speed. parse_server_interfaces() accepts a zero or omitted NETWORK_INTERFACE_INFO::LinkSpeed, and cifs_debug_data_proc_show() divides by the resulting zero minimum speed. A CIFS mount to a malicious or compromised SMB server is required; the kernel oops leaks a held spinlock, deadlocking later CIFS activity, while panic-on-oops configurations shut down the host.

CVSS severity7.5
High
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Divide-by-zero in the Linux CIFS client allows remote attackers controlling an SMB server to interrupt CIFS service through a zero link speed. parse_server_interfaces() accepts a zero or omitted NETWORK_INTERFACE_INFO::LinkSpeed, and cifs_debug_data_proc_show() divides by the resulting zero minimum speed. A CIFS mount to a malicious or compromised SMB server is required; the kernel oops leaks a held spinlock, deadlocking later CIFS activity, while panic-on-oops configurations shut down the host.

The record

CVE
CVE-2025-21725
Published
Feb 27, 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. Feb 27, 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=1cd8c353708de99d8bfa7db8a0c961a800b1fa7f <3f901c35e1a1b3ed1b528a17ffdb941aa0294458
  2. Affected versionversion=548893404c44fc01a59f17727876e02553146fe6 <208e102a2fca44e40a6c3f7b9e2609cfd17a15aa
  3. Affected versionversion=6.1.65 <6.1.129
  4. Affected versionversion=6.6.4 <6.6.76
  5. Affected versionversion=6.7
  6. Affected versionversion=a6d8fb54a515f0546ffdb7870102b1238917e567 <699179dfc8d7da457b152ca5d18ae45f9ed9beaa
  7. Affected versionversion=a6d8fb54a515f0546ffdb7870102b1238917e567 <ad3b49fbdb156aa8ee2026ba590642c9b5a410f2
  8. Affected versionversion=a6d8fb54a515f0546ffdb7870102b1238917e567 <be7a6a77669588bfa5022a470989702bbbb11e7f

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1cd8c353708de99d8bfa7db8a0c961a800b1fa7f <3f901c35e1a1b3ed1b528a17ffdb941aa0294458; version=548893404c44fc01a59f17727876e02553146fe6 <208e102a2fca44e40a6c3f7b9e2609cfd17a15aa; version=6.1.65 <6.1.129; version=6.6.4 <6.6.76; version=6.7; version=a6d8fb54a515f0546ffdb7870102b1238917e567 <699179dfc8d7da457b152ca5d18ae45f9ed9beaa; version=a6d8fb54a515f0546ffdb7870102b1238917e567 <ad3b49fbdb156aa8ee2026ba590642c9b5a410f2; version=a6d8fb54a515f0546ffdb7870102b1238917e567 <be7a6a77669588bfa5022a470989702bbbb11e7f

Published CVSS scores

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

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application 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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