Microsoft today released updates to remedy at least 398 security vulnerabilities in its Windows operating systems and supported software, including one weakness that is already being actively exploited and two others that were publicly detailed prior to today.

August’s overstuffed bundle of patch joy from Microsoft did not eclipse its recording breaking release of more than 570 security updates last month, but it is double June’s then-record batch of nearly 200 fixes. Microsoft has attributed the recent patch deluge to vulnerability discoveries aided by artificial intelligence, and experts roundly agree that Windows users should get used to the idea of Patch Tuesdays (the second Tuesday of each month) covering hundreds of newly discovered security flaws.

Fully 42 of the 398 flaws that Microsoft patched today earned Redmond’s most-dire “critical” rating, meaning they are severe enough that malware or malcontents could exploit them to gain remote control over a Windows computer with little to no help from the user.

The sole known “zero day” bug fixed by Microsoft this month is CVE-2026-68820, a privilege escalation weakness in a core Windows component called afd.sys, which the security firm Automox describes as “the driver behind Windows socket connections on effectively every endpoint.”

“This isn’t a front-door bug,” Automox’s Landon Miles wrote in a Patch Tuesday blog post. “It’s step two in a chain: an attacker phishes their way into a low-privilege foothold, then uses the driver flaw to take the box. The 7.0 score reflects the high attack complexity, because race conditions are fiddly. The exploit has to be thrown over and over until the timing lands. Someone is clearly landing it anyway.”

CVE-2026-62832 is another privilege escalation flaw that Microsoft has labeled likely to be exploited; this flaw, in the Windows User Profile Service, may be related to the recent “LegacyHive” public disclosure from the prolific bug hunter known as Nightmare Eclipse. The other publicly disclosed flaw is CVE-2026-72971, a low-impact local tampering vulnerability that Microsoft reckons is unlikely to be exploited.

Other major software makers are likewise increasing their patch volumes and cadence thanks to AI, including Adobe which last month moved to twice-monthly security bulletins published on the 2nd and 4th Tuesday of each month. Cisco, Google, Mozilla and Oracle also are shipping updates far more frequently and abundantly.

By all accounts, AI is quite good at finding security holes in software. But for now at least, patching the resulting bugpocalypse remains a heavily human-centric endeavor, and the jury is still out on whether AI technologies will turn out to be as good at fixing vulnerabilities as they are at finding and exploiting them. This is an important question when one considers that these same AI technologies also are suggesting fixes for the vulnerabilities they find.

Researchers at 1Password recently examined what happens when different large language models (LLMs) generate vulnerability patches for newly disclosed, complex vulnerabilities. They found the LLMs produced patches that failed to fix the flaw or added a new weakness in the process (or both) more than half the time.

Ed Skoudis, president of the SANS Technology Institute, said his team has seen excellent results using AI to generate patches, provided there are humans in the loop to test the suggested fixes and push for iterative improvements.

“AI is rapidly becoming astonishingly good at finding vulnerabilities, but this research shows that fixing them is a very different problem,” Skoudis wrote in a SANS newsletter today. “Don’t expect one-shot AI patching to work reliably. Instead, iterate, test, challenge, improve, and verify. AI can be an extraordinary patching partner, but today it still needs a skilled human at the keyboard.”

Tyler Reguly at Fortra says while reports of Microsoft patching hundreds of vulnerabilities in one go have prompted some organizations to try to patch faster, it’s important to bear in mind that only one of the almost 400 bugs addressed today is known to be actively exploited. Reguly suggested security leaders check in with their teams to see how they’re handling the increasing workloads, which often involve testing fixes before deploying them in production environments.

“If you’re a chief security officer talk to your teams about how they are shifting or modifying their workflows to better accommodate the patching shift that we’re seeing and support them across various organizational units by enabling the changes they want to see made,” Reguly said. “There’s no need to rush these updates, no matter what various vendors and organizations try to tell you. You need to make sure that you are rolling out safe updates that will not negatively impact your systems.”

Speaking of the humans behind the keyboards, don’t neglect to backup your system and/or data before applying this month’s monster patch load. The day after each month’s Patch Tuesday is sometimes derisively referred to as Reboot Wednesday, but it generally doesn’t hurt to wait a few days to apply these huge update bundles because it sometimes takes a couple of days for the occasional misbehaving patch to get ironed out properly by Microsoft.

For a clickable, per-patch breakdown by severity and urgency, check out this roundup from the SANS Internet Storm Center.

LegacyHive PoC exposes a Windows Privilege Escalation flaw affecting fully patched Windows desktop and server systems.

Just hours after Microsoft’s July 2026 Patch Tuesday, security researcher Nightmare Eclipse, also known as Chaotic Eclipse, published a new Windows zero-day proof-of-concept called LegacyHive. This time, the target is the Windows User Profile Service (ProfSvc), and unlike the hundreds of vulnerabilities Microsoft fixed this month, this one currently has no CVE, no advisory, and no security update.

LegacyHive is a local privilege escalation vulnerability. An attacker who already has code execution as a standard user can abuse the User Profile Service to load another user’s registry hive, potentially that of a local administrator, under their own profile.

That opens the door to accessing registry data that should remain protected and may help elevate privileges under the right conditions. While it isn’t a remote code execution bug, privilege escalation remains one of the most valuable building blocks in modern attack chains.

“The PoC requires another standard user credentials and a third username (which can be an administrator account), if the PoC is successful, it will end up mounting the target user hive in current user classes root.” reads the researcher’s public repository. “The PoC was stripped down as an attempt to prevent public exploitation, the original PoC did not require additional user credential and was not limited to usrclass.dat hive, any hive could be loaded using this vulnerability but you would need some brain cells to make the PoC do it.”

According to the proof-of-concept, exploitation requires several prerequisites. The attacker already needs access to the target system, valid user credentials, and another local user profile whose registry hive can be mounted. That makes LegacyHive unsuitable for mass exploitation over the Internet, but potentially attractive for post-compromise operations where attackers are already inside a network.

The release also continues an increasingly public dispute between Nightmare Eclipse and Microsoft’s Security Response Center (MSRC).

Since April, the researcher has repeatedly published Windows zero-days without coordinated disclosure, arguing that previous reports were mishandled and that researchers were not properly credited. Several of those earlier disclosures were later patched, while some were reportedly exploited before fixes became available.

On June 10, security researcher Chaotic Eclipse published a new working exploit dubbed GreatXML that bypasses BitLocker and opens a command shell with full SYSTEM privileges while Windows is in Recovery Mode. It came one day after RoguePlanet, an exploit targeting Microsoft Defender that leads to local privilege escalation.

Chaotic Eclipse also disclosed BlueHammer (CVE-2026-33825), UnDefend (CVE-2026-45498), and RedSun (CVE-2026-41091) zero-days. The disclosures are believed to stem from a dispute with Microsoft over the vulnerability reporting process.

In early June, Chaotic Eclipse released a PoC for the RoguePlanet Microsoft Defender zero-day, which can grant SYSTEM privileges on fully patched Windows systems.

In May, the researcher disclosed two other Windows zero-day vulnerabilities named YellowKey and GreenPlasma. The flaws affect BitLocker and the Windows Collaborative Translation Framework (CTFMON). YellowKey could allow attackers to bypass BitLocker protections, while GreenPlasma enables privilege escalation. The researcher previously disclosed three Microsoft Defender vulnerabilities.

The researcher criticized Microsoft for revoking access to their MSRC account, rejecting reports, and failing to provide compensation.

At the end of May, Microsoft’s Security Response Center called the zero-day dumps irresponsible.

“In recent weeks several zero-day vulnerabilities have been publicly disclosed.” reads the report published by Microsoft. “The details of these vulnerabilities were not shared with Microsoft prior to release, and the disclosures put our customers at unnecessary risk.”

The company said its security teams have been working around the clock since the disclosures to understand the impact, build patches, and protect customers from attackers who picked up the published exploit code and ran with it.

Microsoft’s post is essentially a public defense of Coordinated Vulnerability Disclosure, the standard practice where a researcher notifies a vendor privately, gives them time to fix the issue, and then goes public. Microsoft says it works with hundreds of researchers this way every year, compensating them through bug bounty programs and crediting them publicly.

“This partnership allows us to make updates to impacted services before proof-of-concept code can make it into the hands of bad actors.” continues the report. “The vulnerabilities known as RedSun, UnDefend, BlueHammer, YellowKey, GreenPlasma, and MiniPlasma were not responsibly disclosed.” 

The implication is clear: when someone skips that step, real people get attacked with real tools built from the published research.

Follow me on Twitter: @securityaffairs and Facebook and Mastodon

Pierluigi Paganini

(SecurityAffairs – hacking, Chaotic Eclipse)

A newly disclosed Windows Defender vulnerability, tracked as CVE-2026-50656 and dubbed RoguePlanet, has raised concerns across the cybersecurity community after a working proof-of-concept (PoC) exploit was released before a security patch became available. The exploit was published on GitHub by security researcher Nightmare Eclipse on June 10, 2026, only hours after Microsoft issued its June Patch Tuesday updates.  The RoguePlanet flaw affects Microsoft Defender and carries a CVSS 3.1 base score of 7.8 (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). It is categorized under CWE-362, which covers race conditions caused by improper synchronization of shared resources. Microsoft has acknowledged CVE-2026-50656 and confirmed that a fix is in development, but as of June 18, 2026, the company has not announced a release timeline. 

Nightmare Eclipse Releases RoguePlanet After Previous Disclosures 

The publication of CVE-2026-50656 followed the researcher’s earlier coordinated disclosures involving two other Defender vulnerabilities, CVE-2026-45586 (GreenPlasma) and CVE-2026-45585 (YellowKey), both of which were addressed during June’s Patch Tuesday cycle.  According to Nightmare Eclipse, the decision to publicly release RoguePlanet without a prior coordinated disclosure period stemmed from dissatisfaction with what the researcher described as slow response times within Microsoft’s bug bounty process. As a result, defenders are now dealing with a publicly documented exploit targeting one of the world’s most widely deployed endpoint security platforms before a patch is available. 

How CVE-2026-50656 Works 

At its core, CVE-2026-50656 exploits a Time-of-Check to Time-of-Use (TOCTOU) race condition inside Microsoft Defender’s file-processing workflow. During a scan, Defender checks a file path and later reopens the file for analysis. The RoguePlanet exploit takes advantage of the gap between those two actions by replacing the original file with a malicious payload. Because Microsoft Defender operates under the SYSTEM account, a successful race condition allows the substituted payload to execute with SYSTEM-level privileges. The exploit reportedly works on fully patched Windows 10 and Windows 11 systems. Although exploitation requires local authenticated access, attackers often obtain such access through phishing campaigns, browser exploits, or stolen credentials. The PoC is not guaranteed to succeed on every attempt because it depends on winning the race condition. However, Nightmare Eclipse noted that automated retry mechanisms can make exploitation reliable in practical scenarios.

Why RoguePlanet Matters 

Local privilege escalation vulnerabilities such as CVE-2026-50656 are frequently used in post-compromise attack chains. Once attackers gain limited access, vulnerabilities like RoguePlanet can elevate permissions to full system control. This enables actions such as disabling security software, extracting credentials from LSASS, establishing persistence, and moving laterally across networks.  Microsoft stated that it is working on a “high-quality patch” but has not committed to an out-of-band release, leaving open the possibility that CVE-2026-50656 could remain unpatched until a future Patch Tuesday update.  Organizations are advised to monitor Windows Event Logs for unexpected SYSTEM-level process creation, deploy EDR detections for rapid file-substitution activity, enforce least-privilege access controls, restrict unnecessary development tools, enable Attack Surface Reduction rules in block mode, block known PoC hashes, and deploy Microsoft’s fix immediately once it becomes available. 

Microsoft today released software updates to plug nearly 200 security holes across its Windows operating systems and supported software, a record number of fixes for the company’s monthly Patch Tuesday cycle. Nearly three dozen of those bugs earned Microsoft’s most dire “critical” rating, and exploit code for at least three of the weaknesses is now publicly available.

The software giant said in a blog post last month that both its engineers and the security community are increasing using artificial intelligence tools to find bugs, meaning this month’s heavy Patch Tuesday may start to become the norm, said Satnam Narang, senior staff research engineer at Tenable.

“Some surveys put AI usage among security professionals generally at 90%, so it’s unsurprising that this volume of patches may be the norm,” Narang said. “Pandora’s proverbial box has been opened, and as more advanced AI models become available, we expect the norm to continue upward across the board, not just for Patch Tuesday.”

June’s zero-day bugs include CVE-2026-49160, a denial of service vulnerability affecting a range of web servers, including Microsoft Internet Information Services (IIS). Microsoft says the flaw was reported by OpenAI’s Codex.

Two of the zero-days addressed this month appear to stem from recent vulnerability disclosures by Nightmare Eclipse, the nickname chosen by a security researcher who has been dropping exploits for various Windows flaws. One of those, dubbed “GreenPlasma,” leverages an elevation of privilege weakness in the Windows Collaborative Translation Framework, the same framework patched today in CVE-2026-45586.

Nightmare Eclipse also last month released “YellowKey,” an exploit for a Windows BitLocker vulnerability that allows an attacker with physical access to view encrypted data, and CVE-2026-50507 is a patch for an elevation of privilege bug in BitLocker.

Microsoft received heavy blowback on social media last month after it said in a blog post that it was considering taking legal action against the security researcher. The company later clarified on Twitter/X that while it has no intention of pursuing legal actions against researchers, it would report them to authorities if they break the law. The advisories for CVE-2026-49160 and CVE-2026-50507 do not credit any researchers in the acknowledgement section, saying only that “Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure.”

Nightmare Eclipse claims to be a former employee of Microsoft, although Microsoft has not responded to questions about this claim. Rapid7 notes that a recent blog post by Nightmare Eclipse included an image of Albert Wesker, a character from the Resident Evil video game series who formerly worked as a researcher for a technology company before going rogue.

Nightmare Eclipse has pledged to release even more zero-day exploits for Windows in what they called a “bone shattering” drop planned for July 14 (the same day as next month’s Patch Tuesday). Immediately following the release of Microsoft patches today, the researcher published an exploit for what they claimed was a zero-day bug in Windows Defender.

While 200 vulnerabilities may be a record for Patch Tuesday, the actual number of security flaws Microsoft addressed this month is far higher, said Rapid7’s Adam Barnett.

“So far this month, Microsoft has provided patches to address 360 browser vulnerabilities, which is an order of magnitude more than has been typical in any given month over the past few years,” Barnett wrote. “As usual, browser [flaws] are not included in the Patch Tuesday count above. Indeed, the vast, and presumably sustained, uptick in the number of browser vulnerabilities has led to Microsoft no longer enumerating Chromium CVEs in the Security Update Guide.”

Microsoft also patched a zero-day vulnerability in Visual Studio Code that allows attackers to steal GitHub tokens with a single click. The company was forced to push a stopgap fix for the flaw on June 3, after a researcher published instructions showing how to exploit it. The researcher said they opted not to work with Microsoft because of a recent experience wherein Redmond silently patched a flaw they reported without offering credit or recognition.

Microsoft battled its own internal zero-day emergencies last week, after at least 72 of the company’s public code repositories were infected with a variant of the Shai-Hulud worm. Researchers found that all of the affected packages were connected to Microsoft official Azure Durable Task SDK, which got hit by the same Shai-Hulud worm in May.

Other major software makers are also shipping outsized update bundles this month. Adobe has released updates to fix a massive number of critical vulnerabilities across a range of products, including Adobe Experience Manager, Acrobat Reader and Cold Fusion. On June 3, Google resolved a whopping 429 vulnerabilities in its latest Chrome browser update (Chrome automatically downloads updates but installing them usually requires a complete restart of the browser).

As ever, please consider backing up your data before applying operating system updates, and drop a note in the comments if you run into any problems with this month’s patches.

Further reading:

Microsoft’s Security Update Guide

Action1’s Patch Tuesday breakdown

SANS Internet Storm Center notes on Patch Tuesday