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Cybercriminals Exploit ASP.NET Vulnerabilities in Stealthy, Sophisticated Attacks
A highly advanced cyber-espionage campaign has come to light, targeting enterprise-level systems across Europe and the United States. Unit 42 researchers have uncovered the tactics of an initial access broker (IAB), identified as TGR-CRI-0045, suspected to be affiliated with the notorious cybercrime syndicate Gold Melody (also known as UNC961 or Prophet Spider). This group has weaponized a unique vulnerability in ASP.NETâs View State mechanism by exploiting leaked Machine Keys, enabling stealthy and highly effective in-memory attacks on critical web infrastructure.
Unlike typical web-based breaches that leave forensic trails, this campaign capitalizes on ASP.NETâs View State deserialization process. When Machine Keys are exposed, they can be used to craft malicious payloads that appear legitimate. TGR-CRI-0045 abused this mechanism to run arbitrary code directly in memory on IIS web servers, effectively bypassing traditional file-based detection tools. Their operations span across sectorsâfinancial services, manufacturing, tech, retail, and transportationâemphasizing the breadth of their campaign.
The group employed open-source tools like ysoserial.net and specifically designed their attacks to be “single-shot”, requiring a fresh exploit for each command execution. Using payloads loaded via the XamlAssemblyLoadFromFile gadget, they were able to load .NET assemblies into memory without leaving behind permanent files. Post-compromise actions included privilege escalation through tools like updf (which leverages the GodPotato exploit), detailed host reconnaissance, and network mapping using scanners like TxPortMap.
What sets this campaign apart is its meticulous defense evasion strategy. The attackers staged tools in a temporary folder (C:\Windows\Temp\111t) and cleaned up afterward to avoid detection. Rather than installing persistent web shells, they relied on repeated in-memory attacks to maintain access, making traditional forensic methods nearly useless.
At least a dozen organizations have already been compromised. According to Unit 42, the root cause in most cases was reused or leaked Machine Keys in ASP.NET applications. These cryptographic keysâintended to ensure data integrityâhave instead become a potent vulnerability when exposed.
To mitigate risk, security experts advise organizations to follow Microsoftâs guidance on rotating and securing Machine Keys, enable View State MAC signing, and implement detailed logging of POST requests. Palo Alto Networks customers have also received updated threat detection capabilities, including enhanced WildFire ML models and improved protections in Cortex XDR and IIS modules.
This campaign stands as a clear warning: even seemingly minor cryptographic missteps can cascade into full-scale breaches when leveraged by sophisticated attackers with the right tools and knowledge.
What Undercode Say:
The Strategic Exploitation of ASP.NETâs Weakest Link
TGR-CRI-0045âs campaign marks a turning point in how attackers manipulate legacy security features for advanced exploitation. At its core, this campaign isn’t about discovering zero-day vulnerabilities, but rather about repurposing existing, trusted mechanismsâspecifically Machine Keysâinto a launchpad for full-scale, memory-based intrusions.
Machine Keys serve a fundamental role in protecting the View State of ASP.NET applications. But once leaked or reused insecurely, they grant an attacker near-unfettered power to impersonate the system’s cryptographic integrity. With these keys, TGR-CRI-0045 generated payloads that bypass normal ASP.NET verification, essentially tricking the system into executing unsigned, malicious commands as if they were safe.
This highlights an essential trend in modern cyberattacks: the shift from static malware to dynamic, ephemeral memory execution. By leveraging open-source tooling and never leaving code on disk, the attackers remain largely invisible to antivirus software and endpoint detection systems that rely on file signatures. The technique also exposes a blind spot in many monitoring solutions, which often neglect in-memory telemetry.
The groupâs use of the XamlAssemblyLoadFromFile gadget in combination with ysoserial.net is another example of layered technical sophistication. These tools allow attackers to embed .NET assemblies that can perform a wide array of post-exploitation tasksâranging from reconnaissance to privilege escalationâwithout ever touching the disk.
Their choice of staging area, C:\Windows\Temp\111t, combined with obfuscated or extensionless filenames, shows how even the simplest tricks can still work when defenders arenât watching the right corners. Furthermore, the deliberate avoidance of persistent implants like web shells signals their intention to reduce dwell time artifacts and maintain operational stealth.
The GodPotato exploit, implemented through the custom updf binary, further illustrates their skillset. By exploiting token impersonation vulnerabilities in Windows, the group elevated privileges to SYSTEMâessentially becoming the most powerful user on the host. This combination of .NET abuse, cryptographic compromise, and privilege escalation represents a well-integrated attack chain rarely seen outside of state-sponsored operations.
From a defensive standpoint, this campaign underscores how outdated or misconfigured cryptographic infrastructure can serve as a ticking time bomb. It’s no longer enough to monitor for malware; security teams must scrutinize even benign features like View State signing, rotating keys regularly, and logging every POST request that could potentially carry a malicious payload.
Moreover, organizations should begin embracing in-memory forensics and behavior-based detection, focusing on anomalies in execution rather than files. The attackâs reliance on serialized payloads that change with every request makes it difficult to pattern-match, further justifying the need for heuristic and behavioral approaches in modern SOCs.
This isnât just an attack on ASP.NET; it’s an attack on trust itselfâtrust in cryptography, in .NET assemblies, and in system memory. If organizations donât update their assumptions and tooling, they’ll continue to leave wide-open backdoors in otherwise “secure” applications.
đ Fact Checker Results:
â Machine Keys are indeed critical to
â TGR-CRI-0045 used in-memory payloads without writing to disk
â At least a dozen known victims were confirmed by Unit 42 researchers
đ Prediction:
As attackers increasingly pivot to in-memory, fileless attack strategies, we predict a sharp rise in cryptographic abuse as a primary access vector in 2025. Organizations still relying on static keys or outdated ASP.NET configurations will become prime targets. Expect future campaigns to weaponize similar trust-based mechanismsâlike JWT signing keys or OAuth tokensâunless organizations adopt zero-trust architecture and dynamic key rotation at scale. đ§ đ
References:
Reported By: cyberpress.org
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