CVE-2025-40099Network attack vector

Kernel heap disclosure and crash via malformed referrals

Published Oct 30, 2025 · Updated Oct 30, 2025

Out-of-bounds read in the Linux kernel CIFS client allows remote attackers to crash clients via malformed SMB DFS referral replies. parse_dfs_referrals trusts OutputCount and NumberOfReferrals, then walks referral entries beyond the received buffer instead of rejecting inconsistent lengths. A client must connect to a malicious, compromised, or man-in-the-middle SMB server; the over-read can expose kernel heap data through the DFS cache or crash the kernel.

CVSS severity9.4
Critical
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

Out-of-bounds read in the Linux kernel CIFS client allows remote attackers to crash clients via malformed SMB DFS referral replies. parse_dfs_referrals trusts OutputCount and NumberOfReferrals, then walks referral entries beyond the received buffer instead of rejecting inconsistent lengths. A client must connect to a malicious, compromised, or man-in-the-middle SMB server; the over-read can expose kernel heap data through the DFS cache or crash the kernel.

The record

CVE
CVE-2025-40099
Published
Oct 30, 2025
Updated
Oct 30, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 30, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 30, 2025Record 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <15c73964da9df994302f579ed14ee5fdbce7a332
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6447b0e355562a1ff748c4a2ffb89aae7e84d2c9
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8bc4a8d39bac23d8b044fd3e2dbfd965f1d9b058
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bb0f2e66e1ac043a5b238f5bcab4f26f3c317039
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cfacc7441f760e4a73cc71b6ff1635261d534657

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <15c73964da9df994302f579ed14ee5fdbce7a332; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6447b0e355562a1ff748c4a2ffb89aae7e84d2c9; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8bc4a8d39bac23d8b044fd3e2dbfd965f1d9b058; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bb0f2e66e1ac043a5b238f5bcab4f26f3c317039; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cfacc7441f760e4a73cc71b6ff1635261d534657

Published CVSS scores

5.5Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
9.4Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/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

T1499.004Application 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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