CVE-2025-21748Network attack vector

Kernel memory corruption via 32-bit allocation overflow

Published Feb 27, 2025 · Updated Aug 5, 2026

Integer overflow in ksmbd in affected Linux kernel releases starting at 5.15 allows remote attackers to corrupt kernel memory via SMB. The ipc_msg_alloc() helper adds attacker-controlled message lengths on 32-bit systems without first bounding the total, so the wrapped allocation is smaller than the subsequent memcpy length. A reachable ksmbd service on TCP port 445 and a 32-bit kernel are required; exploitation overwrites adjacent kernel heap objects and can crash the host or redirect kernel control flow.

CVSS severity9.8
Critical
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in ksmbd in affected Linux kernel releases starting at 5.15 allows remote attackers to corrupt kernel memory via SMB. The ipc_msg_alloc() helper adds attacker-controlled message lengths on 32-bit systems without first bounding the total, so the wrapped allocation is smaller than the subsequent memcpy length. A reachable ksmbd service on TCP port 445 and a 32-bit kernel are required; exploitation overwrites adjacent kernel heap objects and can crash the host or redirect kernel control flow.

The record

CVE
CVE-2025-21748
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-190, T1190
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=0626e6641f6b467447c81dd7678a69c66f7746cf <760568c1f62ea874e8fb492f9cfa4f47b4b8391e
  2. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <82f59d64e6297f270311b16b5dcf65be406d1ea3
  3. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <aab98e2dbd648510f8f51b83fbf4721206ccae45
  4. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <b4b902737746c490258de5cb55cab39e79927a67
  5. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <ecb9947fa7c99a77b04d43404c6988a0d326e4a0
  6. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <f3b9fb2764591d792d160f375851013665a9e820
  7. Affected versionversion=5.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0626e6641f6b467447c81dd7678a69c66f7746cf <760568c1f62ea874e8fb492f9cfa4f47b4b8391e; version=0626e6641f6b467447c81dd7678a69c66f7746cf <82f59d64e6297f270311b16b5dcf65be406d1ea3; version=0626e6641f6b467447c81dd7678a69c66f7746cf <aab98e2dbd648510f8f51b83fbf4721206ccae45; version=0626e6641f6b467447c81dd7678a69c66f7746cf <b4b902737746c490258de5cb55cab39e79927a67; version=0626e6641f6b467447c81dd7678a69c66f7746cf <ecb9947fa7c99a77b04d43404c6988a0d326e4a0; version=0626e6641f6b467447c81dd7678a69c66f7746cf <f3b9fb2764591d792d160f375851013665a9e820; version=5.15

Published CVSS scores

9.8Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.5NIST National Vulnerability DatabaseCVSS: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.

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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-190Integer Overflow or Wraparound
T1190Exploit Public-Facing Application

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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