CVE-2025-21648

Service interruption via oversized conntrack resize

Published Jan 19, 2025 · Updated Sep 8, 2026

Excessive memory allocation in Linux kernel netfilter conntrack allows local users to interrupt service by resizing its hash table. The resize path accepts a size above INT_MAX and passes the oversized request to __kvmalloc_node_noprof without __GFP_NOWARN, triggering WARN_ON_ONCE. Only a user able to resize the table from the initial network namespace can reach the condition, and the documented consequence is availability loss.

CVSS severity5.5
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Excessive memory allocation in Linux kernel netfilter conntrack allows local users to interrupt service by resizing its hash table. The resize path accepts a size above INT_MAX and passes the oversized request to __kvmalloc_node_noprof without __GFP_NOWARN, triggering WARN_ON_ONCE. Only a user able to resize the table from the initial network namespace can reach the condition, and the documented consequence is availability loss.

The record

CVE
CVE-2025-21648
Published
Jan 19, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-789, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 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=V3.1.6 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*
Siemens · SIMATIC S7-1500 TM MFP - GNU/Linux subsystemversion=0 <*
The Linux Kernel Organization · Linuxversion=4.7; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <5552b4fd44be3393b930434a7845d8d95a2a3c33; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <a965f7f0ea3ae61b9165bed619d5d6da02c75f80; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <b1b2353d768f1b80cd7fe045a70adee576b9b338; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <b541ba7d1f5a5b7b3e2e22dc9e40e18a7d6dbc13; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <d5807dd1328bbc86e059c5de80d1bbee9d58ca3d; version=9cc1c73ad66610bffc80b691136ffc1e9a3b1a58 <f559357d035877b9d0dcd273e0ff83e18e1d46aa
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.1Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
5.5Siemens ProductCERTCVSS: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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-789Memory Allocation with Excessive Size Value
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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