Microsoft as we speak 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 below 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 printed zero-day vulnerabilities on Patch Tuesday with out evaluating any of them as crucial severity at time of publication. Immediately additionally noticed the publication of 9 crucial distant code execution (RCE) vulnerabilities.
The Microsoft flaws already seeing energetic assaults embrace 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 element that’s closely embedded in fashionable Home windows 11 working techniques and used for safety features together with system 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 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 varied 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 need to 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 as we speak earned CVSS (risk score) 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 sometimes opened on Workplace purposes like Microsoft Phrase. Microsoft has rated this flaw “exploitation extra doubtless.”
Bob Hopkins at Immersive Labs referred to 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 vital information or expertise to attain repeatable success with the identical payload throughout any susceptible element,” Hopkins wrote.
Kev Breen at Immersive factors to an attention-grabbing 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 likelihood that in some conditions the hibernation picture created when one closes the laptop computer lid on an open Home windows session is probably not absolutely encrypted and might be recovered in plain textual content.
“Hibernation photographs are used when a laptop computer goes to sleep and incorporates the contents that had been saved in RAM in the mean time the system powered down,” Breen famous. “This presents a big potential impression as RAM can include delicate information (reminiscent of 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 searching for 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 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 person who has computerized updates turned off and haven’t up to date shortly, it’s in all probability time to play catch up. Please think about backing up essential recordsdata and/or the complete exhausting drive earlier than updating. And in case you run into any issues putting in this month’s patch batch, drop a line within the feedback under, please.
Additional studying on as we speak’s patches from Microsoft:
