CVE-2026-109107 Overview
CVE-2026-109107 is a null pointer dereference vulnerability in the Wavlink WL-WN592AX6 wireless range extender running firmware version 250422. The flaw resides in the main function of /cgi-bin/upload.cgi and is triggered by manipulating the HTTP Cookie argument. A remote, unauthenticated attacker can send a crafted request to crash the handling process. Public exploit details are available, increasing the likelihood of opportunistic abuse against exposed devices. The weakness is categorized under CWE-404 (Improper Resource Shutdown or Release).
Critical Impact
Remote attackers can trigger a null pointer dereference in upload.cgi without authentication, causing availability loss on affected Wavlink extenders.
Affected Products
- Wavlink WL-WN592AX6 wireless range extender
- Firmware version 250422
- The /cgi-bin/upload.cgi CGI binary
Discovery Timeline
- 2026-10-13 - CVE-2026-109107 published to the National Vulnerability Database (NVD)
- 2026-10-13 - Last updated in NVD database
Technical Details for CVE-2026-109107
Vulnerability Analysis
The vulnerability affects the main function of /cgi-bin/upload.cgi, a CGI handler exposed by the device's embedded web server. The handler reads the Cookie HTTP header and uses the resulting value without validating that the pointer is non-null. When the attacker-controlled Cookie argument is absent or malformed, the subsequent dereference operates on a null pointer and the process terminates. Because the CGI binary is invoked by the web server for incoming requests, repeated exploitation disrupts the management interface and any routed service that depends on it.
Root Cause
The root cause is improper resource handling in the main entry point of upload.cgi. The code path assumes the Cookie header produces a valid string pointer and omits a null check before dereferencing. This maps to [CWE-404], where program resources are not released or validated correctly, resulting in an avoidable crash when the input is unexpected.
Attack Vector
Exploitation requires only network access to the device's HTTP interface. An unauthenticated attacker sends a crafted HTTP request to /cgi-bin/upload.cgi with a manipulated or missing Cookie header. No user interaction is required. Where the device's web interface is reachable from untrusted networks, the attack can be performed directly from the internet. Public exploit information is available via VulDB CVE-2026-109107.
No verified proof-of-concept code is reproduced here. See VulDB Vulnerability #416858 for technical details.
Stop Remote Code Execution Before It Runs
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Stop Exploit AttemptsDetection Methods for CVE-2026-109107
Indicators of Compromise
- Unexpected restarts or crash logs referencing the upload.cgi process on Wavlink WL-WN592AX6 devices.
- HTTP requests to /cgi-bin/upload.cgi with absent, empty, or malformed Cookie headers from unfamiliar source addresses.
- Repeated 5xx responses or connection resets from the device's management interface.
Detection Strategies
- Inspect web server and CGI logs on the extender for repeated access to /cgi-bin/upload.cgi followed by process termination.
- Deploy network intrusion detection signatures that flag anomalous Cookie headers directed at Wavlink management URIs.
- Correlate device availability loss with inbound HTTP traffic to management ports in your SIEM.
Monitoring Recommendations
- Forward device syslog and HTTP access logs to a centralized logging platform for retention and correlation.
- Monitor administrative interfaces for sudden drops in reachability or elevated error rates.
- Alert on unauthenticated access attempts to CGI endpoints from external network segments.
How to Mitigate CVE-2026-109107
Immediate Actions Required
- Restrict access to the device's web management interface to trusted management VLANs only.
- Block inbound internet access to the extender's HTTP and HTTPS ports at the perimeter firewall.
- Inventory Wavlink WL-WN592AX6 devices running firmware 250422 and prioritize them for remediation.
Patch Information
No vendor advisory or fixed firmware release is referenced in the published CVE data at the time of writing. Monitor the Wavlink support site and VulDB CVE-2026-109107 for updated firmware availability.
Workarounds
- Disable remote management on the WAN interface of the extender.
- Place the device behind a network segment that filters unsolicited HTTP traffic.
- Replace end-of-life or unpatched hardware with supported alternatives where a firmware fix is not available.
# Example: block external access to the device management interface
# Replace <device_ip> and <mgmt_subnet> with your values
iptables -A FORWARD -d <device_ip> -p tcp --dport 80 -s <mgmt_subnet> -j ACCEPT
iptables -A FORWARD -d <device_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <device_ip> -p tcp --dport 443 -s <mgmt_subnet> -j ACCEPT
iptables -A FORWARD -d <device_ip> -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
