CVE-2026-40434: Anviz CrossChex Standard DoS Vulnerability

CVE-2026-40434 Overview

Anviz CrossChex Standard lacks source verification in the client/server channel, enabling TCP packet injection by an attacker on the same network to alter or disrupt application traffic. This vulnerability (CWE-940: Improper Verification of Source of a Communication Channel) allows adjacent network attackers to inject malicious TCP packets into legitimate communication streams, potentially compromising the integrity of time and attendance management operations.

Critical Impact

Adjacent network attackers can inject or alter TCP traffic between CrossChex Standard clients and servers, potentially manipulating attendance records, disrupting access control operations, or causing denial of service to the time management system.

Affected Products

• Anviz CrossChex Standard (all versions prior to patched release)

Discovery Timeline

• 2026-04-17 - CVE-2026-40434 published to NVD
• 2026-04-20 - Last updated in NVD database

Technical Details for CVE-2026-40434

Vulnerability Analysis

The vulnerability stems from Anviz CrossChex Standard's failure to properly verify the source of incoming communications in its client/server architecture. This security weakness allows an attacker positioned on the same network segment to inject arbitrary TCP packets into the communication channel between legitimate clients and the server.

CrossChex Standard is time and attendance management software used in conjunction with Anviz biometric devices for workforce management. The lack of source verification means the application does not validate whether incoming packets originate from authorized clients, creating an opportunity for packet injection attacks.

This vulnerability requires the attacker to have adjacent network access (such as being on the same LAN or VLAN), but once positioned, no privileges or user interaction are required to exploit the flaw. Successful exploitation can result in high impact to both integrity and availability of the application.

Root Cause

The root cause is Improper Verification of Source of a Communication Channel (CWE-940). The CrossChex Standard application does not implement adequate authentication or validation mechanisms to verify that TCP packets received on its communication channel originate from legitimate, authorized sources. This absence of source verification allows attackers to spoof or inject packets that appear to be from valid clients.

Attack Vector

The attack requires adjacent network positioning, allowing an attacker on the same local network to perform TCP packet injection. The attacker can:

1. Monitor network traffic between CrossChex clients and servers
2. Craft malicious TCP packets mimicking legitimate communication patterns
3. Inject these packets into the communication stream
4. Manipulate application data or disrupt service availability

Since no authentication is required and no user interaction is needed, exploitation is straightforward for an attacker with network access. The attack can alter legitimate traffic flows, inject false commands, or disrupt normal operations through packet flooding or malformed packet injection.

Detection Methods for CVE-2026-40434

Indicators of Compromise

• Unusual TCP packet patterns or unexpected source addresses communicating with CrossChex Standard server ports
• Anomalous network traffic volumes on segments where Anviz CrossChex devices communicate
• Discrepancies in attendance records or access logs that don't match physical observations
• Connection resets or communication failures between CrossChex clients and servers

Detection Strategies

• Implement network traffic analysis to identify anomalous TCP packet patterns targeting CrossChex Standard communication channels
• Deploy intrusion detection systems (IDS) with rules to detect TCP packet injection attempts on the local network segment
• Monitor for MAC address spoofing or ARP poisoning attempts that often precede packet injection attacks
• Review CrossChex application logs for authentication failures or unexpected command sequences

Monitoring Recommendations

• Enable detailed logging on CrossChex Standard servers and review logs regularly for anomalies
• Implement network segmentation monitoring to detect unauthorized devices on segments containing CrossChex infrastructure
• Deploy SentinelOne Singularity™ Platform for endpoint protection and network traffic analysis capabilities
• Establish baseline network behavior for CrossChex communications to identify deviations

How to Mitigate CVE-2026-40434

Immediate Actions Required

• Isolate Anviz CrossChex Standard servers and clients on a dedicated, segmented network with strict access controls
• Implement network-level authentication (802.1X) to prevent unauthorized devices from accessing the CrossChex network segment
• Deploy additional encryption layers such as VPN tunnels for CrossChex client/server communications
• Contact Anviz through their contact page for information on patched versions

Patch Information

Refer to the CISA ICS Advisory ICSA-26-106-03 for official guidance and patch availability. Additional technical details can be found in the GitHub CSAF JSON file. Organizations should monitor Anviz official channels for firmware and software updates that address this vulnerability.

Workarounds

• Implement strict network segmentation to limit adjacent network access to CrossChex systems
• Deploy network access control (NAC) solutions to authenticate all devices before granting network access
• Use VLAN segregation with ACLs to restrict which hosts can communicate with CrossChex servers
• Consider implementing IPsec or TLS wrappers around CrossChex communications as an additional protection layer