Play Ransomware Group Exploits Windows Zero-Day Vulnerability: What You Need to Know

Microsoft’s April 2025 security update quietly contained a patch for a critical Windows zero-day vulnerability — but not before multiple ransomware groups had already used it in live attacks. One of these groups, known as Balloonfly (associated with the Play ransomware operation), leveraged the flaw in an attempt to penetrate systems, install custom malware, and set the stage for more destructive activity. With growing concerns around state-sponsored and financially motivated cyber threats, this discovery highlights once again how fast threat actors weaponize vulnerabilities before organizations can respond.

This article explores the technical details of CVE-2025-29824, the actors behind the attacks, and the broader implications for cybersecurity strategy in 2025. It also includes exclusive analytical commentary and predictions from Undercode.

the Attack: Play Ransomware Meets Windows Zero-Day

The Zero-Day: The exploited vulnerability, tracked as CVE-2025-29824, is a post-compromise privilege escalation flaw in the Windows Common Log File System Driver, scoring 7.8 on the CVSS scale.
Patch Timing: Microsoft patched it in April 2025, but the flaw had already been exploited in the wild prior to the update.
Primary Actor Identified: Initially attributed to a group named Storm-2460, which used the bug to deploy ransomware in multiple countries including the US, Venezuela, Spain, and Saudi Arabia.
New Exploiter Found: Symantec identified Balloonfly (aka Play ransomware group) also using the vulnerability against a US-based target — this occurred before the patch was released.
Payload Details: In this intrusion, Grixba, a custom infostealer, was deployed along with other malware. Files mimicked legitimate software like Palo Alto Networks tools (e.g., paloaltoconfig.exe).
Attack Vectors: Access may have originated via a Cisco firewall exposed to the public internet, then pivoted laterally to infect a secondary Windows system using CVE-2025-29824.
Technical Differentiation: Unlike Storm-2460, who used a fileless, in-memory exploit, Balloonfly employed a disk-based method, showing variations in attack sophistication and style.
Why It Matters: Post-compromise privilege escalation vulnerabilities are critical as they allow threat actors to solidify control and move laterally inside victim networks before ransomware deployment.
Microsoft Advisory: Urged immediate patching and emphasized prioritizing elevation-of-privilege vulnerabilities, which are increasingly central to modern ransomware tactics.
About Balloonfly: Active since mid-2022, known for double extortion, intermittent encryption, and targeting critical infrastructure globally.
Tactics & Tools: Frequently use tools like Cobalt Strike, Mimikatz, ProcDump, AdFind, and WinPEAS for lateral movement and data theft.
Victim Profile: Mostly mid-sized organizations, but also includes critical infrastructure and government entities in countries such as the US, Italy, and Australia.
Evading Detection: One of Play’s most dangerous traits is its ability to blend in using legitimate system tools, making it challenging for defenders to identify breaches in real time.

What Undercode Say:

The exploitation of CVE-2025-29824 by multiple adversaries before a public patch underlines a chronic issue in cybersecurity: patch lag vs. attacker speed. Vulnerabilities like this, while technically “post-compromise,” often become the linchpin of ransomware operations once the initial access has been secured. This incident proves that modern ransomware groups aren’t just script kiddies running off-the-shelf payloads — they’re adaptive, modular, and willing to develop or acquire zero-day exploits to stay ahead.

Balloonfly’s approach in this case is notably strategic. Instead of dropping ransomware immediately, they deployed Grixba, an infostealer, likely to map out high-value targets before deploying their extortion playbook. This suggests that groups are moving towards longer dwell times and more complex intrusions rather than smash-and-grab encryption.

The use of disguised malware samples (e.g., naming files like Palo Alto software) is a clever obfuscation tactic. Combined with legitimate tools like