Microsoft immediately unleashed updates to plug a whopping 161 safety vulnerabilities in Home windows and associated software program, together with three “zero-day” weaknesses which can be already beneath lively assault. Redmond’s inaugural Patch Tuesday of 2025 bundles extra fixes than the corporate has shipped in a single go since 2017.
Rapid7‘s Adam Barnett says January marks the fourth consecutive month the place Microsoft has printed zero-day vulnerabilities on Patch Tuesday with out evaluating any of them as essential severity at time of publication. Right now additionally noticed the publication of 9 essential distant code execution (RCE) vulnerabilities.
The Microsoft flaws already seeing lively assaults embody CVE-2025-21333, CVE-2025-21334 and, you guessed it– CVE-2025-21335. These are sequential as a result of all reside in Home windows Hyper-V, a part that’s closely embedded in trendy Home windows 11 working programs and used for security measures together with system guard and credential guard.
Tenable’s Satnam Narang says little is thought concerning the in-the-wild exploitation of those flaws, other than the truth that they’re all “privilege escalation” vulnerabilities. Narang mentioned we are likely to see lots of elevation of privilege bugs exploited within the wild as zero-days in Patch Tuesday as a result of it’s not all the time preliminary entry to a system that’s a problem for attackers as they’ve numerous avenues of their pursuit.
“As elevation of privilege bugs, they’re getting used as a part of post-compromise exercise, the place an attacker has already accessed a goal system,” he mentioned. “It’s type of like if an attacker is ready to enter a safe constructing, they’re unable to entry safer components of the ability as a result of they should show that they’ve clearance. On this case, they’re capable of trick the system into believing they need to have clearance.”
A number of bugs addressed immediately earned CVSS (risk ranking) scores of 9.8 out of a attainable 10, together with CVE-2025-21298, a weak point in Home windows that would enable attackers to run arbitrary code by getting a goal to open a malicious .rtf file, paperwork usually opened on Workplace purposes like Microsoft Phrase. Microsoft has rated this flaw “exploitation extra probably.”
Bob Hopkins at Immersive Labs referred to as consideration to the CVE-2025-21311, a 9.8 “essential” bug in Home windows NTLMv1 (NT LAN Supervisor model 1), an older Microsoft authentication protocol that’s nonetheless utilized by many organizations.
“What makes this vulnerability so impactful is the truth that it’s remotely exploitable, so attackers can attain the compromised machine(s) over the web, and the attacker doesn’t want important data or expertise to realize repeatable success with the identical payload throughout any weak part,” Hopkins wrote.
Kev Breen at Immersive factors to an fascinating flaw (CVE-2025-21210) that Microsoft fastened in its full disk encryption suite Bitlocker that the software program big has dubbed “exploitation extra probably.” Particularly, this bug holds out the chance that in some conditions the hibernation picture created when one closes the laptop computer lid on an open Home windows session might not be totally encrypted and might be recovered in plain textual content.
“Hibernation pictures are used when a laptop computer goes to sleep and incorporates the contents that had been saved in RAM for the time being the system powered down,” Breen famous. “This presents a big potential affect as RAM can include delicate information (resembling passwords, credentials and PII) which will have been in open paperwork or browser classes and may all be recovered with free instruments from hibernation information.”
Tenable’s Narang additionally highlighted a trio of vulnerabilities in Microsoft Entry fastened this month and credited to Unpatched.ai, a safety analysis effort that’s aided by synthetic intelligence searching for vulnerabilities in code. Tracked as CVE-2025-21186, CVE-2025-21366, and CVE-2025-21395, these are distant code execution bugs which can be exploitable if an attacker convinces a goal to obtain and run a malicious file via social engineering. Unpatched.ai was additionally credited with discovering a flaw within the December 2024 Patch Tuesday launch (CVE-2024-49142).
“Automated vulnerability detection utilizing AI has garnered lots of consideration lately, so it’s noteworthy to see this service being credited with discovering bugs in Microsoft merchandise,” Narang noticed. “It might be the primary of many in 2025.”
If you happen to’re a Home windows consumer who has automated updates turned off and haven’t up to date shortly, it’s most likely time to play catch up. Please think about backing up essential information and/or your entire onerous drive earlier than updating. And if you happen to run into any issues putting in this month’s patch batch, drop a line within the feedback under, please.
Additional studying on immediately’s patches from Microsoft:
