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Microsoft on Sunday released security patches for an actively exploited security flaw in SharePoint and also disclosed details of another vulnerability that it said has been addressed with "more robust protections." The tech giant acknowledged it's "aware of active attacks targeting on-premises SharePoint Server customers by exploiting vulnerabilities partially addressed by the July Security Update." CVE-2025-53770 (CVSS score: 9.8), as the exploited vulnerability is tracked, concerns a case of remote code execution that arises due to the deserialization of untrusted data in on-premise versions of Microsoft SharePoint Server. The newly disclosed shortcoming is a spoofing flaw in SharePoint ( CVE-2025-53771 , CVSS score: 7.1). Viettel Cyber Security and an anonymous researcher has been credited with discovering and reporting the bug. "Improper limitation of a pathname to a restricted directory ('path traversal') in Microsoft Office SharePoint...

A critical security vulnerability in Microsoft SharePoint Server has been weaponized as part of an "active, large-scale" exploitation campaign. The zero-day flaw, tracked as CVE-2025-53770 (CVSS score: 9.8), has been described as a variant of CVE-2025-49704 (CVSS score: 8.8), a code injection and remote code execution bug in Microsoft SharePoint Server that was addressed by the tech giant as part of its July 2025 Patch Tuesday updates. "Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network," Microsoft said in an advisory released on July 19, 2025. The Windows maker further noted that it's preparing and fully testing a comprehensive update to resolve the issue. It credited Viettel Cyber Security for discovering and reporting the flaw through Trend Micro's Zero Day Initiative (ZDI). In a separate alert issued Saturday, Redmond said it's aware of active attacks ta...

Security researchers found a way to enter Microsoft SharePoint servers as any user, including an administrator, with no valid account. A significant part of the work that found it was done through an AI agent. The flaw, tracked as  CVE-2026-55040  (CVSS 9.1), affects SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016. Microsoft's affected-product list covers only those three on-premises editions, and SharePoint Online is not among them. It lets a remote unauthenticated attacker assume a chosen user's identity. The attack has one prerequisite: the intruder has to know which account they want to become, either by its Active Directory security identifier (SID) or its user principal name (UPN), which is formatted like an email address. Rapid7 then chained the bypass to a separate remote code execution flaw and ran code on the server with no credentials. Microsoft and the firm disclosed that second flaw on August 11 as  CVE-2026...

The recently disclosed critical Microsoft SharePoint vulnerability has been under exploitation as early as July 7, 2025, according to findings from Check Point Research. The cybersecurity company said it observed first exploitation attempts targeting an unnamed major Western government, with the activity intensifying on July 18 and 19, spanning government, telecommunications, and software sectors in North America and Western Europe. Check Point also said the exploitation efforts originated from three different IP addresses – 104.238.159[.]149, 107.191.58[.]76, and 96.9.125[.]147 – one of which was previously tied to the weaponization of security flaws in Ivanti Endpoint Manager Mobile (EPMM) appliances ( CVE-2025-4427 and CVE-2025-4428 ). "We're witnessing an urgent and active threat: a critical zero-day in SharePoint on-prem is being exploited in the wild, putting thousands of global organizations at risk," Lotem Finkelstein, Director of Threat Intelligence at Chec...

Phishing works no matter how hard a company tries to protect its customers or employees. Security researchers have been warning of a new phishing attack that cybercriminals and email scammers are using in the wild to bypass the Advanced Threat Protection (ATP) mechanism implemented by widely used email services like Microsoft Office 365. Microsoft Office 365 is an all-in-solution for users that offers several different online services, including Exchange Online, SharePoint Online, Lync Online and other Office Web Apps, like Word, Excel, PowerPoint, Outlook and OneNote. On the top of these services, Microsoft also offers an artificial intelligence and machine learning powered security protection to help defend against potential phishing and other threats by going one level deep to scan the links in the email bodies to look for any blacklisted or suspicious domain. But as I said, phishers always find a way to bypass security protections in order to victimize users. Just ...

Microsoft has formally tied the exploitation of security flaws in internet-facing SharePoint Server instances to two Chinese hacking groups called Linen Typhoon and Violet Typhoon as early as July 7, 2025 , corroborating earlier reports. The tech giant said it also observed a third China-based threat actor, which it tracks as Storm-2603, weaponizing the flaws as well to obtain initial access to target organizations. "With the rapid adoption of these exploits, Microsoft assesses with high confidence that threat actors will continue to integrate them into their attacks against unpatched on-premises SharePoint systems," the tech giant said in a report published today. A brief description of the threat activity clusters is below - Linen Typhoon (aka APT27 , Bronze Union, Emissary Panda, Iodine, Lucky Mouse, Red Phoenix, and UNC215), which is active since 2012 and has been previously attributed to malware families like SysUpdate, HyperBro, and PlugX Violet Typhoon (aka ...

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Thursday added a newly patched security flaw impacting Microsoft SharePoint Server to its Known Exploited Vulnerabilities ( KEV ) catalog, requiring Federal Civilian Executive Branch (FCEB) agencies to apply the fixes by July 19, 2026. The vulnerability in question is CVE-2026-58644 (CVSS score: 9.8), a critical deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute arbitrary code. "In a network-based attack, an attacker authenticated as at least a Site Owner, could write arbitrary code to inject and execute code remotely on the SharePoint Server," Microsoft said in an advisory released earlier this week. Redmond noted that the vulnerability is remotely exploitable over the internet, warning that the attack complexity is low for two reasons - An attacker does not require significant prior knowledge of the system An attacker can achieve repeatable su...

The U.S. Cybersecurity and Infrastructure Security Agency (CISA), on July 22, 2025, added two Microsoft SharePoint flaws, CVE-2025-49704 and CVE-2025-49706, to its Known Exploited Vulnerabilities ( KEV ) catalog, based on evidence of active exploitation. To that end, Federal Civilian Executive Branch (FCEB) agencies are required to remediate identified vulnerabilities by July 23, 2025. "CISA is aware of active exploitation of a spoofing and RCE vulnerability chain involving CVE-2025-49706 and CVE-2025-49704, enabling unauthorized access to on-premise SharePoint servers," the agency said in an updated advisory. The inclusion of the two shortcomings, a spoofing vulnerability and a remote code execution vulnerability collectively tracked as ToolShell, to the KEV catalog comes after Microsoft revealed that Chinese hacking groups like Linen Typhoon and Violet Typhoon leveraged these flaws to breach on-premises SharePoint servers since July 7, 2025. As of writing, the tech...

A third SharePoint Server flaw patched by Microsoft as part of its Patch Tuesday update for July 2026 has come under active exploitation, per watchTowr . The vulnerability in question is CVE-2026-50522 (CVSS score: 9.8), a critical deserialization of untrusted data in Microsoft Office SharePoint that could allow an unauthorized attacker to execute code over a network. Microsoft credited DEVCORE researcher "splitline" with discovering and reporting the flaw. "In a network-based attack, an attacker authenticated as at least a Site Owner, could write arbitrary code to inject and execute code remotely on the SharePoint Server," Redmond said in an advisory released last week. "The attack vector is Network (AV:N) because this vulnerability is remotely exploitable and can be exploited from the internet. The attack complexity is Low (AC:L) because an attacker does not require significant prior knowledge of the system and can achieve repeatable success with the ...

Security researcher Chaotic Eclipse (aka Nightmare-Eclipse ) has released a new proof-of-concept (PoC) exploit called LegacyHive. It has been described as a Windows User Profile Service arbitrary hive load elevation of privileges vulnerability. The Windows User Profile Service, also referred to as ProfSvc, is a core system component that manages user accounts and environments. "The PoC requires another standard user credential and a third username (which can be an administrator account)," Chaotic Eclipse said . "If the PoC is successful, it will end up mounting the target user hive in the current user classes root." The researcher said the exploit was stripped down to prevent public exploitation, adding the original exploit did not require additional user credentials and was not limited to the "usrclass.dat" hive. "Any hive could be loaded using this vulnerability, but you would need some brain cells to make the PoC do it," the researc...

Microsoft has revealed that one of the threat actors behind the active exploitation of SharePoint flaws is deploying Warlock ransomware on targeted systems. The tech giant, in an update shared Wednesday, said the findings are based on an "expanded analysis and threat intelligence from our continued monitoring of exploitation activity by Storm-2603 ." The threat actor attributed to the financially motivated activity is a suspected China-based threat actor that's known to drop Warlock and LockBit ransomware in the past. The attack chains entail the exploitation of CVE-2025-49706, a spoofing vulnerability, and CVE-2025-49704, a remote code execution vulnerability, targeting unpatched on-premises SharePoint servers to deploy the spinstall0.aspx web shell payload. "This initial access is used to conduct command execution using the w3wp.exe process that supports SharePoint," Microsoft said. "Storm-2603 then initiates a series of discovery commands, incl...

Threat actors have begun to exploit a newly disclosed Microsoft SharePoint vulnerability following the release of a proof-of-concept (PoC) code. The vulnerability in question is CVE-2026-55040 (CVSS score: 9.1), which refers to a critical security feature bypass that stems from weak authentication. It was patched by Microsoft as part of its July 2026 Patch Tuesday updates. "The authentication feature could be bypassed as this vulnerability allows impersonation," Microsoft said in an advisory for the flaw last month. "Exploiting this vulnerability could allow an attacker to disclose files and modify data, but the attacker cannot impact the availability of the system." According to Defused Cyber , threat actors are leveraging a PoC exploit released by Rapid7 earlier this week, once again indicating fresh flaws are being rapidly abused in real-world attacks. It's worth mentioning that CVE-2026-55040 is the fifth SharePoint vulnerability to be exploited t...

Cybersecurity researchers have disclosed details of a now-patched vulnerability impacting the Microsoft SharePoint connector on Power Platform that, if successfully exploited, could allow threat actors to harvest a user's credentials and stage follow-on attacks. This could manifest in the form of post-exploitation actions that allow the attacker to send requests to the SharePoint API on behalf of the impersonated user, enabling unauthorized access to sensitive data, Zenity Labs said in a report shared with The Hacker News ahead of publication. "This vulnerability can be exploited across Power Automate, Power Apps, Copilot Studio, and Copilot 365, which significantly broadens the scope of potential damage," senior security researcher Dmitry Lozovoy said . "It increases the likelihood of a successful attack, allowing hackers to target multiple interconnected services within the Power Platform ecosystem." Following responsible disclosure in September 2024, ...

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Wednesday added a high-severity flaw impacting Microsoft SharePoint Server to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerability, tracked as CVE-2026-45659 (CVSS score: 8.8), is a case of remote code execution arising from the deserialization of untrusted data. The issue was addressed by Microsoft in May 2026 for SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Enterprise Server 2016. Microsoft noted that any authenticated attacker could trigger the vulnerability, and that it does not require admin or other elevated privileges. In a network-based attack, an authenticated attacker with a minimum of Site Member permissions (PR:L) could leverage it to execute code remotely on the SharePoint Server. "Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker t...

Microsoft has rolled out updates to fix a remote code execution vulnerability impacting SharePoint that could be exploited by bad actors in attacks without requiring any specialized conditions to be met. The vulnerability, tracked as CVE-2026-45659 , carries a CVSS score of 8.8. It has been assigned an important severity. "Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network," Microsoft said in an advisory released last week. Microsoft noted that the vulnerability could be triggered by any authenticated attacker, and that it does not require administrator or other elevated privileges. "In a network-based attack, an authenticated attacker, who has a minimum of Site Member permissions (PR:L), could execute code remotely on the SharePoint Server," the Windows maker added. Microsoft credited a researcher named MEOW for discovering and reporting the flaw. Updates have been released for th...

Microsoft shipped its largest Patch Tuesday on record today, and two of the fixes close holes that attackers are already exploiting. The release covers 622 of Microsoft's own CVEs by its  Security Update Guide  count, more than triple  June's previous high of around 200 . Those two live bugs are the ones to grab first. Microsoft credits incident responders for both. Both are elevation-of-privilege flaws in identity and collaboration infrastructure: CVE-2026-56164 in on-premises SharePoint Server and CVE-2026-56155 in Active Directory Federation Services. Neither is one of the splashy remote code execution criticals. They are privilege bugs in two systems that matter more than their scores suggest: the company document store, and the box that signs its logins. The two zero-days to patch first CVE-2026-56164 , a SharePoint Server flaw Microsoft says is being exploited in attacks, lets an unauthenticated attacker escalate privileges over the ne...

As part of its "October Patch Tuesday," Microsoft has today released a large batch of security updates to patch a total of 62 vulnerabilities in its products, including a severe MS office zero-day flaw that has been exploited in the wild. Security updates also include patches for Microsoft Windows operating systems, Internet Explorer, Microsoft Edge, Skype, Microsoft Lync and Microsoft SharePoint Server. Besides the MS Office vulnerability, the company has also addressed two other publicly disclosed (but not yet targeted in the wild) vulnerabilities that affect the SharePoint Server and the Windows Subsystem for Linux. October patch Tuesday also fixes a critical Windows DNS vulnerability that could be exploited by a malicious DNS server to execute arbitrary code on the targeted system. Below you can find a brief technical explanation of all above mentioned critical and important vulnerabilities. Microsoft Office Memory Corruption Vulnerability (CVE-2017-11826) T...

As part of this month's Patch Tuesday, Microsoft today released a fresh batch of security updates to fix a total of 129 newly discovered security vulnerabilities affecting various versions of its Windows operating systems and related software. Of the 129 bugs spanning its various products — Microsoft Windows, Edge browser, Internet Explorer, ChakraCore, SQL Server, Exchange Server, Office, ASP.NET, OneDrive, Azure DevOps, Visual Studio, and Microsoft Dynamics — that received new patches, 23 are listed as critical, 105 are important, and one is moderate in severity. Unlike the past few months, none of the security vulnerabilities the tech giant patched in September are listed as being publicly known or under active attack at the time of release or at least not in knowledge of Microsoft. A memory corruption vulnerability ( CVE-2020-16875 ) in Microsoft Exchange software is worth highlighting all the critical flaws. The exploitation of this flaw could allow an attacker to run ...

Microsoft released its monthly security updates on Tuesday, and one of the flaws it closed is already being used in attacks. The bug sits in a core Windows kernel driver that handles network socket operations. An attacker with code already running on a machine can use it to escalate to SYSTEM. That patch goes out first. The flaw is tracked as CVE-2026-68820 (CVSS score: 7.0) and is the only one in this month's release Microsoft flags as under active exploitation. Exploitation depends on triggering a race condition in the driver. Microsoft has not publicly attributed the exploitation. Check Point Research says Lazarus used the zero-day in its Operation Dream Job campaign. Four other flaws in the release need nothing at all from the victim: no account, no password, no click. They affect Windows DNS Server, Windows Deployment Services, Microsoft's implementation of the QUIC transport protocol, and High Performance Computing (HPC) Pack, and each carries a CVSS score of 9.8....

Cybersecurity researchers have disclosed details of a previously undocumented Python implant framework dubbed TWINLOOT . "TWINLOOT is a modular, PyArmor-hardened Python implant designed to operate its entire command-and-control infrastructure inside trusted Microsoft services," Ontinue said in a technical report shared with The Hacker News. "Tasking flows through SharePoint Online file dead-drops via the Microsoft Graph API. Interactive operator access routes through WebRTC DataChannels relayed by Microsoft Teams TURN servers." Traffic to and from the Graph API is driven by means of a headless instance of the victim's own Edge browser, thereby making it virtually indistinguishable from legitimate network activity. The implant is equipped to harvest Windows credentials using pixel-perfect fake lock screens, offer a reverse SOCKS5 pivot into victim networks, execute arbitrary commands, and establish persistence on the host. Ontinue's Cyber Defense Cen...