CVE-2025-38191Network attack vector

Remote host crash via null session user

Published Jul 4, 2025 · Updated Aug 5, 2026

NULL pointer dereference in Linux ksmbd allows remote attackers to crash the host through a crafted Kerberos SMB session setup. destroy_previous_session dereferences a null sess->user before ksmbd_krb5_authenticate initializes it when PreviousSessionId is set. An unauthenticated network client can reach the path without user interaction, causing a kernel crash and service interruption.

CVSS severity7.5
High
EPSS probability1.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux ksmbd allows remote attackers to crash the host through a crafted Kerberos SMB session setup. destroy_previous_session dereferences a null sess->user before ksmbd_krb5_authenticate initializes it when PreviousSessionId is set. An unauthenticated network client can reach the path without user interaction, causing a kernel crash and service interruption.

The record

CVE
CVE-2025-38191
Published
Jul 4, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 4, 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=0626e6641f6b467447c81dd7678a69c66f7746cf <076f1adefb9837977af7ed233883842ddc446644
  2. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <0902625a24eea7fdc187faa5d97df244d159dd6e
  3. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <1193486dffb7432a09f57f5d09049b4d4123538b
  4. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <281afc52e2961cd5dd8326ebc9c5bc40904c0468
  5. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <7ac5b66acafcc9292fb935d7e03790f2b8b2dc0e
  6. Affected versionversion=5.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0626e6641f6b467447c81dd7678a69c66f7746cf <076f1adefb9837977af7ed233883842ddc446644; version=0626e6641f6b467447c81dd7678a69c66f7746cf <0902625a24eea7fdc187faa5d97df244d159dd6e; version=0626e6641f6b467447c81dd7678a69c66f7746cf <1193486dffb7432a09f57f5d09049b4d4123538b; version=0626e6641f6b467447c81dd7678a69c66f7746cf <281afc52e2961cd5dd8326ebc9c5bc40904c0468; version=0626e6641f6b467447c81dd7678a69c66f7746cf <7ac5b66acafcc9292fb935d7e03790f2b8b2dc0e; version=5.15

Published CVSS scores

5.9TrendAI Zero Day InitiativeCVSS:3.1/AV:N/AC:H/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
7.5kernel.orgCVSS: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 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

CWE-476NULL Pointer Dereference
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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