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Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2025-56234

HIGH · 7.5 CVSS v3.1 Published 2025-09-29
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
AT_NA2000 from Nanda Automation Technology vendor has a denial-of-service vulnerability. For the processing of TCP RST packets, PLC AT_NA2000 has a wide acceptable range of sequence numbers. It does not require the sequence number to exactly match the next expected sequence value, just to be within the current receive window, which violates RFC5961. This flaw allows attackers to send multiple random TCP RST packets to hit the acceptable range of sequence numbers, thereby interrupting normal connections and causing a denial-of-service attack.

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 · high confidence

The AT_NA2000 PLC from Nanda Automation Technology improperly validates TCP RST packet sequence numbers by accepting any sequence value within the current receive window rather than requiring an exact match to the next expected sequence number, violating RFC5961 blind RST attack mitigation. This allows attackers to brute-force valid sequence numbers by sending multiple random TCP RST packets, causing legitimate connections to be terminated and resulting in denial of service.

MitigationImplement network segmentation and firewall rules to restrict unauthorized access to the PLC's TCP ports; consult vendor for firmware patches that enforce proper RFC5961 sequence number validation.

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 AT_NA2000 PLC on the network
    Use network scanning tools such as nmap, or check your asset inventory/SCADA system for devices with the identifier 'AT_NA2000' or manufacturer 'Nanda Automation Technology'. Inspect DHCP logs, PLC programming software (e.g., Nanda Automation's configuration tool), or physical device labeling.
    Affected if The target environment contains an AT_NA2000 PLC device.
  2. Determine the PLC firmware version
    Access the PLC via its web interface (if available), serial console, or vendor-specific management software. Look for a firmware version field in the device status or system information page. If unavailable via UI, consult the vendor documentation for commands via PLC programming software to retrieve the firmware revision.
    Affected if The installed firmware version matches or falls within the vendor's affected version range (if published), or the version cannot be determined and the device is exposed.
  3. Verify network accessibility of PLC TCP ports
    Perform a port scan (e.g., nmap -p- <PLC_IP>) from a testing host to enumerate open TCP ports on the PLC. Common PLC ports include 80 (HTTP), 502 (Modbus), and vendor-proprietary ports. Compare against your expected configuration.
    Affected if The PLC has accessible TCP ports reachable from network segments that contain untrusted or attacker-adjacent hosts.
  4. Check for network segmentation and firewall rules
    Review firewall rules, VLAN configurations, or network ACLs that govern traffic between the PLC and other network zones. Use network diagrams or firewall rule exports to verify that only authorized management stations and HMIs can reach the PLC's TCP ports.
    Affected if The PLC's TCP ports are reachable from zones without explicit trust relationships, indicating lack of adequate network segmentation.
  5. Inspect for anomalous connection terminations
    Review PLC or network device logs (firewall, switch, IDS) for patterns of unexpected TCP RST packets or connection drops affecting the PLC. Correlate timestamps with any recent network events or security incidents.
    Affected if Logs show repeated or unusual TCP connection resets targeting the PLC that cannot be attributed to normal operations.

A user is affected if their environment contains an AT_NA2000 PLC with firmware in the vulnerable version range (or unverifiable version) and the device's TCP ports are network-accessible from untrusted segments, allowing potential blind RST injection attacks.

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 restrict unauthorized access to the PLC's TCP ports; consult vendor for firmware patches that enforce proper RFC5961 sequence number validation.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,980
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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-2025-56234 in production — separate from our analysis above.

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What this is

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What belongs here
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