CVE-2024-23113 (Fortinet Multiple Products Format String)

What this vulnerability means in practice

CVE-2024-23113 is dangerous because a remote, unauthenticated request can trigger code or command execution in exposed Fortinet management or security appliances. In products that sit on the network edge, that can turn a single parsing flaw into full device compromise.

Format string flaws are especially serious when they occur in internet-facing infrastructure because the vulnerable input is processed before normal authentication or authorization checks can help. For a practitioner, the key question is not only whether the product is present, but whether it is reachable from untrusted networks or exposed through a partner path.

Why format string bugs are so high impact

A format string vulnerability lets attacker-controlled data be interpreted as formatting instructions instead of plain text. That can corrupt memory, leak process state, or steer execution, which is why these bugs are often associated with arbitrary code execution rather than a simple crash.

In appliances, the business impact is amplified by the role of the affected system. If the device mediates remote access, web traffic, administration, or security enforcement, compromise can affect every session or workload that depends on it. The same defect can therefore become both an initial access path and a staging point for broader intrusion.

How organisations should assess exposure and reduce immediate risk

Exposure review starts with an accurate asset inventory, then narrows to which Fortinet products are deployed, which interfaces are enabled, and whether management or user-facing services are reachable from the internet. Vendor advisories and the NIST National Vulnerability Database should be checked alongside the CVE Program record for authoritative identifiers and remediation references.

When patching cannot happen immediately, reduce the attack surface by restricting exposure, limiting administrative paths, tightening allowlists, and placing compensating controls around any externally reachable instance. If the appliance is essential, treat it as a high-priority asset and verify whether traffic filtering or segmentation can remove the vulnerable entry point until remediation is complete.

Detection, remediation, and post-exploitation review

Because the flaw was added to CISA’s Known Exploited Vulnerabilities catalogue, organisations should assume there is real-world exploitation pressure and verify whether the product was contacted by suspicious requests before or after patching. Review logs for unusual request patterns, unexpected command execution indicators, configuration changes, new accounts, altered credentials, or persistence on the device.

Post-patch review matters because fixing the software does not prove the appliance was not already abused. Where compromise is plausible, investigate for follow-on actions such as stolen credentials, modified trust material, or outbound connections that suggest the device was used as a foothold. If the appliance mediated authentication or admin access, rotate any credentials, tokens, or keys that may have been exposed during the incident.

Risk and Threat Considerations

Exploited format string flaws on edge appliances are attractive because they can bypass normal user authentication, deliver high privileges, and often sit in front of sensitive services. That makes the risk more than a single vulnerable host, it can become a gateway to broader network compromise, credential theft, and operational disruption.

Failure mechanism: An attacker sends a crafted request that reaches vulnerable parsing code, causes memory corruption or unsafe execution, and then uses the resulting control to run commands or implant persistence.

Impact: The appliance may be used to intercept traffic, steal secrets, tamper with access controls, pivot deeper into the environment, or disrupt security and remote-access services.

Practitioner Guidance

What to watch for: Treat any CVE with KEV status as an exposure-management priority, not a routine backlog item. For internet-facing Fortinet devices, confirm ownership, verify reachability, and establish who can approve emergency containment when patching is delayed.

Practitioner takeaway: If the device is exposed, assumed-safe until proven otherwise is the wrong default, because actively exploited appliance flaws often change from vulnerability management problems into incident-response problems very quickly.

Related resources from NHI Mgmt Group

• CVE-2025-59718 (Fortinet Multiple Products Improper Verification of Cryptographic Signature)
• CVE-2025-25249 (Fortinet Multiple Products Heap-based Buffer Overflow)
• CVE-2025-32756 (Fortinet Multiple Products Stack-Based Buffer Overflow)
• CVE-2024-55956 (Cleo Multiple Products Unauthenticated File Upload)