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NULL Pointer DereferenceWeakness · CWE-476

CVE-2025-40833

HIGH · 7.5 CVSS v3.1 Published 2026-05-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The affected devices contain a null pointer dereference vulnerability while processing specially crafted IPv4 requests. This could allow an attacker to cause denial of service condition. A manual restart is required to recover the system.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Affected devices contain a null pointer dereference vulnerability when processing specially crafted IPv4 packets. An attacker sending malformed IPv4 requests can trigger the null pointer dereference, causing the device to crash and require a manual restart to recover.

MitigationImplement network segmentation and firewall rules to limit exposure to untrusted IPv4 traffic; apply vendor patches when available and consider intrusion detection to identify exploitation attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device software version
    Access the device management interface (CLI, web UI, or SNMP) and retrieve the installed firmware/software version using commands like 'show version', 'system info', or equivalent for your device type. Document this version number.
    Affected if The installed version matches the version range where the vulnerability exists (compare your version to any vendor-advisory version ranges)
  2. Verify IPv4 packet processing is enabled
    Check the device configuration for active IPv4 interfaces and routing. Use commands like 'show ip interface', 'show ip config', or review the web UI network settings to confirm IPv4 is operational.
    Affected if IPv4 processing is enabled and the device is actively handling IPv4 traffic - the vulnerability only triggers when IPv4 packets are processed
  3. Assess network exposure to untrusted IPv4 traffic
    Review firewall rules, ACLs, and interface configurations to determine if the device's IPv4 interfaces are directly reachable from untrusted networks (WAN, DMZ, or external networks). Check for proper filtering on inbound interfaces.
    Affected if The device accepts IPv4 packets from untrusted or external sources without adequate filtering
  4. Inspect for crash logs or unexpected restarts
    Review system logs, crash dumps, and boot logs for any entries around the time of unexpected behavior. Look for patterns like 'null pointer', 'kernel panic', 'crash', 'restart', or 'reboot' in log files.
    Affected if Logs indicate device crashes or restarts that coincide with suspicious IPv4 traffic patterns
  5. Check for existing IPv4 traffic anomalies
    Monitor IPv4 traffic statistics and counters on ingress interfaces. Look for unusual packet rates, fragment anomalies, or malformed packet indicators using 'show ip traffic', 'show interface counters', or network monitoring tools.
    Affected if Abnormal or malformed IPv4 traffic patterns are observed entering the device

You are affected if your device runs a vulnerable software version, has IPv4 processing enabled, and is exposed to untrusted IPv4 traffic that could contain the crafted packets.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement network segmentation and firewall rules to limit exposure to untrusted IPv4 traffic; apply vendor patches when available and consider intrusion detection to identify exploitation attempts.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-40833 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data