Today we’re speaking with Dominic Jainy, a technologist whose work at the intersection of AI and blockchain has given him a unique perspective on complex system security. We’re diving deep into a critical vulnerability in FortiSIEM, a flaw that isn’t just a simple bug but a devastating two-stage exploit chain. We’ll explore how attackers can move from zero access to complete root control, the architectural weaknesses that enable these attacks, the clever techniques used to bypass security measures, and what the early interest from ransomware groups like Black Basta means for defenders on the ground.
An attacker can chain an argument injection with a file overwrite to gain root on FortiSIEM. Can you walk through this two-stage process, detailing how they first achieve admin access and then escalate to achieve full root compromise on the system?
It’s a devastatingly simple and effective chain. The attack begins with a completely unauthenticated request to the phMonitor service listening on TCP port 7900. The attacker crafts a specific API message targeting the handleStorageRequest function, embedding malicious commands within XML tags. This initial foothold is an argument injection that cleverly uses curl to overwrite a system binary, /opt/phoenix/bin/phLicenseTool, with a reverse shell. Since this tool is executed regularly, the attacker gains code execution as the ‘admin’ user. From there, it’s a short hop to full control. The ‘admin’ user has write permissions on a shell script, /opt/charting/redishb.sh, which is executed by a root cronjob every single minute. The attacker simply overwrites this script with their own payload, waits for the cronjob to run, and they achieve a root shell, completely compromising the entire SIEM platform.
The phMonitor service on port 7900 appears to be a persistent weak point in FortiSIEM’s architecture. Based on its design, why does this unauthenticated service present such a recurring attack surface, and what fundamental hardening steps should be taken beyond just patching?
That’s the core of the problem. The phMonitor service was designed for inter-role communication in a distributed deployment, but its fatal flaw is that it processes these custom API messages without any authentication. The logic essentially maps an integer in the request to a specific command handler, creating a massive, exposed attack surface. We’ve seen this service targeted before with CVE-2023-34992 for the exact same reason. Simply patching the individual vulnerable handlers is like playing whack-a-mole. The fundamental hardening required is architectural. Access to port 7900 must be strictly firewalled to only allow communication between trusted supervisor and collector nodes. Beyond that, the service itself needs an authentication layer. Relying on network segmentation alone is a fragile defense; the service should be secure by design, not by deployment.
This exploit creatively uses curl’s obscure --next flag to bypass security wrappers. Can you elaborate on this specific argument injection technique and what its success reveals about the challenges of properly sanitizing user input passed to complex shell scripts?
This is the most elegant part of the exploit and a real lesson for developers. The system uses wrappers like subprocess.run() and wrapShellToken to try and escape or sanitize user input before it’s passed to the elastic_test_url.sh script. The developers likely anticipated simple injections. However, the attacker leverages curl‘s --next flag, which allows for multiple URL operations in a single command line. Their injected cluster_url contains the initial benign URL, followed by --next and then a malicious -o argument to write a file. The security wrapper sees a single, seemingly valid argument, but curl interprets it as two separate commands. It reveals a classic blind spot: you can’t possibly sanitize for every obscure feature of every complex command-line tool you call. This is why it’s so critical to avoid passing raw user input to shell commands whenever possible and to operate with the least privilege necessary.
For security teams hunting for this threat, what specific PHL_ERROR entries should they search for in /opt/phoenix/log/phoenix.logs? Please detail a step-by-step process for how an analyst could confirm a compromise by examining both the logs and key system files.
An analyst needs to dive into /opt/phoenix/log/phoenix.logs. The key indicator is a PHL_ERROR entry related to the elastic_test_url.sh script failing. The log will contain the malicious URL the attacker used, which will be a dead giveaway because it will include the --next flag and the file output argument, for instance, -o /opt/phoenix/bin/phLicenseTool. So, the first step is to grep those logs for elastic_test_url.sh and look for any unusual command structures. To confirm, the analyst should immediately check the modification time and hash of /opt/phoenix/bin/phLicenseTool. If it’s been recently modified or doesn’t match a known-good version, it’s almost certainly compromised. The final step is to inspect the /etc/cron.d/fsm-crontab to verify the root cronjob and then examine the script it runs, /opt/charting/redishb.sh, for any malicious payloads.
Leaked chats suggest the Black Basta ransomware group was interested in this vulnerability before it was widely publicized. What does this tell us about their operational methods, and how should this early threat actor interest influence the patching priority for defenders managing SIEMs?
This detail sends a chill down your spine. It shows that sophisticated threat actors like Black Basta aren’t just waiting for public proof-of-concept exploits to drop on GitHub. They have their own vulnerability discovery channels, whether through in-house research or dark web marketplaces. They are proactive, not reactive. For a defender, this completely changes the risk calculation. It means the moment a CVE is announced, even without public details, you have to assume that motivated attackers are already working to weaponize it. When the target is your SIEM—the central nervous system of your security operations—this intelligence should escalate the patching priority to the absolute highest level. It’s not a routine patch; it’s an emergency response to a known and active threat from a top-tier adversary.
What is your forecast for the security of SIEM platforms?
I foresee SIEM platforms becoming even more valuable targets for attackers. These systems are the crown jewels for a security team, aggregating sensitive logs and threat data from across an entire enterprise. Compromising the SIEM not only blinds the defenders but also provides attackers with a roadmap of the network’s defenses and weaknesses. As a result, we’ll see more exploits like this one that target complex, often under-audited management services and APIs. Vendors will face immense pressure to move toward a “secure by default” architecture, with robust authentication on all internal services and a drastic reduction in attack surface. For organizations, the security of their security tools must become a top priority, not an afterthought.