Microsoft has revealed {that a} now-patched security flaw impacting the Home windows Widespread Log File System (CLFS) was exploited as a zero-day in ransomware assaults geared toward a small variety of targets.
“The targets embrace organizations within the data know-how (IT) and actual property sectors of the US, the monetary sector in Venezuela, a Spanish software program firm, and the retail sector in Saudi Arabia,” the tech big mentioned.
The vulnerability in query is CVE-2025-29824, a privilege escalation bug in CLFS that might be exploited to realize SYSTEM privileges. It was mounted by Redmond as a part of its Patch Tuesday replace for April 2025.
Microsoft is monitoring the exercise and the post-compromise exploitation of CVE-2025-29824 beneath the moniker Storm-2460, with the risk actors additionally leveraging a malware named PipeMagic to ship the exploit in addition to ransomware payloads.
The precise preliminary entry vector used within the assaults is at the moment not recognized. Nonetheless, the risk actors have been noticed utilizing the certutil utility to obtain malware from a reputable third-party website that was beforehand compromised to stage the payloads.
The malware is a malicious MSBuild file that accommodates an encrypted payload, which is then unpacked to launch PipeMagic, a plugin-based trojan that has been detected within the wild since 2022.
It is value mentioning right here that CVE-2025-29824 is the second Home windows zero-day flaw to be delivered by way of PipeMagic after CVE-2025-24983, a Home windows Win32 Kernel Subsystem privilege escalation bug, which was flagged by ESET and patched by Microsoft final month.
Beforehand, PipeMagic was additionally noticed in reference to Nokoyawa ransomware assaults that exploited one other CLFS zero-day flaw (CVE-2023-28252).
“In a number of the different assaults that we attribute to the identical actor, we additionally noticed that, previous to exploiting the CLFS elevation-of-privilege vulnerability, the sufferer’s machines have been contaminated with a customized modular backdoor named ‘PipeMagic’ that will get launched by way of an MSBuild script,” Kaspersky identified in April 2023.
It is essential to notice that Home windows 11, model 24H2, just isn’t affected by this particular exploitation, as entry to sure System Data Lessons inside NtQuerySystemInformation grew to become obtainable solely to customers with SeDebugPrivilege, which generally solely admin-like customers can receive.
“The exploit targets a vulnerability within the CLFS kernel driver,” the Microsoft Risk Intelligence crew defined. “The exploit then makes use of a reminiscence corruption and the RtlSetAllBits API to overwrite the exploit course of’s token with the worth 0xFFFFFFFF, enabling all privileges for the method, which permits for course of injection into SYSTEM processes.”
Profitable exploitation is adopted by the risk actor extracting person credentials by dumping the reminiscence of LSASS and encrypting recordsdata on the system with a random extension.
Microsoft mentioned it was unable to acquire a ransomware pattern for evaluation, however mentioned that the ransom be aware dropped after encryption included a TOR area tied to the RansomEXX ransomware household.
“Ransomware risk actors worth post-compromise elevation of privilege exploits as a result of these may allow them to escalate preliminary entry, together with handoffs from commodity malware distributors, into privileged entry,” Microsoft mentioned. “They then use privileged entry for widespread deployment and detonation of ransomware inside an surroundings.”
