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 might be already underneath energetic 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 revealed zero-day vulnerabilities on Patch Tuesday with out evaluating any of them as crucial severity at time of publication. At the moment additionally noticed the publication of 9 crucial distant code execution (RCE) vulnerabilities.
The Microsoft flaws already seeing energetic 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 fashionable Home windows 11 working programs and used for safety features together with gadget guard and credential guard.
Tenable’s Satnam Narang says little is thought in regards to the in-the-wild exploitation of those flaws, aside from the truth that they’re all “privilege escalation” vulnerabilities. Narang stated we are inclined to see a number of elevation of privilege bugs exploited within the wild as zero-days in Patch Tuesday as a result of it’s not at all times 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 stated. “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 must 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 (menace ranking) scores of 9.8 out of a potential 10, together with CVE-2025-21298, a weak spot in Home windows that might enable attackers to run arbitrary code by getting a goal to open a malicious .rtf file, paperwork usually opened on Workplace functions like Microsoft Phrase. Microsoft has rated this flaw “exploitation extra doubtless.”
Bob Hopkins at Immersive Labs known as consideration to the CVE-2025-21311, a 9.8 “crucial” 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 information or abilities to attain 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 doubtless.” 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 comprises the contents that have been saved in RAM in the meanwhile the gadget powered down,” Breen famous. “This presents a big potential impression as RAM can include delicate information (corresponding to passwords, credentials and PII) which will have been in open paperwork or browser classes and might all be recovered with free instruments from hibernation recordsdata.”
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 in search of vulnerabilities in code. Tracked as CVE-2025-21186, CVE-2025-21366, and CVE-2025-21395, these are distant code execution bugs which might be exploitable if an attacker convinces a goal to obtain and run a malicious file by means of 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 a number of consideration not too long ago, so it’s noteworthy to see this service being credited with discovering bugs in Microsoft merchandise,” Narang noticed. “It could be the primary of many in 2025.”
Should you’re a Home windows consumer who has automated updates turned off and haven’t up to date shortly, it’s in all probability time to play catch up. Please take into account backing up vital recordsdata and/or the whole arduous 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:
