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CVE-2026-24641 is a NULL pointer dereference vulnerability (CWE-476) residing within the Anti-Defacement feature of Fortinet FortiWeb. The flaw allows an authenticated attacker, who already possesses valid credentials, to send specially crafted HTTP requests to the affected device. When the FortiWeb’s HTTP daemon processes these malicious requests, a failure in pointer validation leads to a dereference of a NULL pointer. This action causes the HTTP daemon process to crash unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability impacts a wide range of FortiWeb versions, including 8.0.0 through 8.0.2, 7.6.0 through 7.6.6, and all versions of 7.4, 7.2, and 7.0. As the vulnerability requires authentication, the attack surface is limited to trusted users, which contributes to its lower severity rating. However, if exploited, it can disrupt web application firewall services, leaving protected web applications temporarily exposed. The issue stems from improper handling of input within the Anti-Defacement mechanism, where the software fails to ensure a pointer is valid before using it to reference memory. This classic programming error can be triggered remotely over the network. No public exploit is currently available, but the technical details are sufficient for a motivated attacker to develop one. Fortinet has acknowledged the vulnerability and recommends applying the available security updates to mitigate the risk. The vulnerability was officially published on March 10, 2026, with subsequent updates to the advisory.
dailycve form:
Platform: Fortinet FortiWeb
Version: 8.0.0-8.0.2,7.6.0-7.6.6,7.4-7.0
Vulnerability: NULL Pointer Dereference
Severity: Low
date: 03/10/2026
Prediction: Immediate vendor update
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Example of a crafted HTTP request that might trigger the NULL pointer dereference (Conceptual - specific exploit details are not public) curl -i -s -k -X $'POST' \ -H $'Host: target.fortiweb.local' -H $'Content-Type: application/x-www-form-urlencoded' \ --data-binary $'action=check&defacement_id=\x00\x00\x00\x00' \ $'https://target.fortiweb.local/api/v2.0/anti_defacement/check' Command to check the current FortiWeb version via CLI ssh admin@<FortiWeb_IP> "get system status | grep Version" Command to verify if the HTTP daemon is running after an exploit attempt ssh admin@<FortiWeb_IP> "diagnose sys process list | grep httpd"
How Exploit:
An authenticated attacker sends a series of HTTP requests with malformed parameters to the Anti-Defacement API endpoint. The application, failing to validate a pointer derived from this input, attempts to use a NULL pointer, causing the httpd process to crash and denying service to legitimate users .
Protection from this CVE
Immediately update FortiWeb to a patched version provided by Fortinet. As a temporary workaround, restrict access to the Anti-Defacement feature to only trusted administrative IP addresses and monitor logs for unusual HTTP request patterns targeting that functionality.
Impact:
Successful exploitation leads to a crash of the HTTP daemon, resulting in a temporary denial of service for the web application firewall. This leaves backend web applications unprotected during the downtime and disrupts legitimate traffic inspection.
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Sources:
Reported By: nvd.nist.gov
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