CVE-2025-40833: IPv4 Null Pointer Dereference Triggers DoS
The National Vulnerability Database (NVD) has released details on CVE-2025-40833, a high-severity vulnerability (CVSS 7.5) affecting unspecified devices. The flaw, categorized as CWE-476 (Null Pointer Dereference), allows an unauthenticated attacker to trigger a denial-of-service (DoS) condition by sending specially crafted IPv4 requests.
This isn’t a theoretical issue; a successful exploit forces a complete system shutdown. Recovery isn’t automatic; it requires a manual restart of the affected device. While the NVD has not specified affected products or vendors, the broad nature of IPv4 processing means many network devices could potentially be vulnerable. This type of vulnerability is a low-effort, high-impact win for attackers looking to disrupt operations.
For defenders, the lack of specific product information is a major challenge. This is a classic ‘unknown unknown’ scenario. Any device processing IPv4 traffic at a fundamental level could be at risk. The attacker’s calculus is simple: send malformed packets, watch systems drop, and force manual intervention. This is a prime target for basic disruption campaigns or as a smokescreen for more sophisticated attacks.
What This Means For You
- If your organization operates critical infrastructure or services that rely on continuous network availability, you need to assume this vulnerability could impact you. Proactively audit all network devices that handle IPv4 traffic for any available patches or vendor advisories related to null pointer dereference issues. Implement robust network segmentation and ingress filtering to mitigate the impact of malformed traffic.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
CVE-2025-40833: IPv4 Null Pointer Dereference DoS Attempt
title: CVE-2025-40833: IPv4 Null Pointer Dereference DoS Attempt
id: scw-2026-05-12-ai-1
status: experimental
level: high
description: |
This rule detects potential exploitation attempts targeting CVE-2025-40833. The vulnerability involves specially crafted IPv4 requests leading to a null pointer dereference and Denial of Service. This rule specifically looks for traffic directed to port 4 (often associated with IPv4 control messages or malformed packets) from internal source IPs to internal destination IPs, which could indicate an internal threat actor or a compromised internal system attempting to exploit this vulnerability.
author: SCW Feed Engine (AI-generated)
date: 2026-05-12
references:
- https://shimiscyberworld.com/posts/nvd-CVE-2025-40833/
tags:
- attack.impact
- attack.t1499
logsource:
category: firewall
detection:
selection:
dst_port:
- 4
src_ip|contains:
- '192.168.'
dst_ip|contains:
- '10.0.'
condition: selection
falsepositives:
- Legitimate administrative activity
Source: Shimi's Cyber World · License & reuse
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2025-40833 | DoS | Null Pointer Dereference |
| CVE-2025-40833 | DoS | Specially crafted IPv4 requests |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | May 12, 2026 at 13:16 UTC |
This content was AI-rewritten and enriched by Shimi's Cyber World based on the original source. All intellectual property rights remain with the original author.
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