Microsoft Releases Urgent Patch for SharePoint RCE Flaw Exploited in Ongoing Cyber Attacks
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2025-49704 +1 in the same advisory: …49706 | Authenticated Code Injection RCE in Microsoft SharePoint CVE-2025-49704 is a code injection vulnerability (CWE-94) in Microsoft SharePoint that allows an authorized (authenticated) attacker to execute arbitrary code on the server over the network, by sending requests whose attacker-controlled input SharePoint executes as code. It can be chained with CVE-2025-49706, and Microsoft subsequently issued CVE-2025-53770 as a patch bypass of the original CVE-2025-49704 fix, meaning the CVE-2025-53770 updates provide stronger protection and should be treated as the definitive remediation. Successful exploitation yields remote code execution on the SharePoint server, and CISA added the flaw to the KEV on 2025-07-22 with known ransomware use. Organizations running on-premises SharePoint Server are affected; CISA directs owners of public-facing servers running EOL/EOS versions (SharePoint Server 2013 and earlier) to disconnect them, and operators of supported versions to apply the CISA and vendor mitigations and updates, with cloud SharePoint services governed by BOD 22-01. Exploitation is confirmed in the wild and EPSS assigns a 100% probability of exploitation within 30 days (top percentile), although no public proof-of-concept code is documented. Do: Apply Microsoft's SharePoint Server updates for CVE-2025-53770, which supersede the original CVE-2025-49704 fixes with more robust protection, prioritizing internet-facing servers. Disconnect public-facing SharePoint servers running EOL/EOS versions (SharePoint Server 2013 and earlier), and for supported versions follow the CISA and vendor mitigations, with cloud services handled per BOD 22-01. Because in-the-wild exploitation and ransomware use are confirmed, hunt for indicators of compromise and ransomware activity on exposed SharePoint servers. | 8.8 group max | 100% | KEV ransomware |
| masstens of thousands of internet-exposed SharePoint servers per public scans, within a total on-premises install base plausibly exceeding 100,000 deployments… | |
| CVE-2025-53770 | Unauthenticated Deserialization RCE in Microsoft SharePoint Server on-premises CVE-2025-53770 is a deserialization of untrusted data vulnerability (CWE-502) in Microsoft SharePoint Server on-premises that allows an unauthorized attacker to execute code over a network. It is triggered when the server deserializes attacker-controlled data, can be chained with CVE-2025-53771, and it bypasses the fixes issued for CVE-2025-49704, meaning the earlier patches are insufficient. Successful exploitation yields remote code execution on the SharePoint server, and ransomware operators are known to be using it. Any organization running SharePoint Server on-premises is affected, particularly internet-facing deployments and end-of-life versions such as SharePoint Server 2013 and earlier that can no longer be patched. The flaw is being actively exploited — it was added to CISA's KEV on 2025-07-20 with known ransomware use — and EPSS assigns it a 100% probability of exploitation within 30 days. Do: Apply Microsoft's updated SharePoint Server security updates that fix CVE-2025-53770 — these include more robust protection than the earlier CVE-2025-49704 updates — and ensure the companion CVE-2025-53771 is also addressed, following CISA and vendor mitigation instructions for supported versions. Disconnect public-facing SharePoint Server 2013 or earlier (EOL/EOS) instances, minimize internet exposure of supported servers, and hunt for signs of compromise given the known ransomware exploitation. | 9.8 | 100% | KEV ransomware PoC ×3 |
| mass≈25,000–100,000 internet-exposed on-premises SharePoint servers (public internet-wide scans); total on-prem installed base plausibly >1M users | |
| CVE-2025-53771 | Improper Authentication in Microsoft SharePoint Server Enables Network Spoofing CVE-2025-53771 is an improper authentication flaw (CWE-287) in Microsoft's on-premises SharePoint Server that allows an unauthenticated remote attacker to conduct spoofing over the network. Per the CVSS vector, exploitation requires no privileges and no user interaction, so an attacker who can reach the SharePoint server over the network can trigger it directly. Successful exploitation lets the attacker impersonate an authenticated user or component, producing limited but real impact on confidentiality and integrity (CVSS 6.5, medium). Any organization running on-premises SharePoint Server is affected, particularly those exposing it to the internet; no specific version numbers are provided in the source data, so defenders should consult Microsoft's advisory for their edition. No public PoC exists and it is not yet in CISA's KEV, but exploitation likelihood is near-certain (EPSS 99.7%, 100th percentile), and Microsoft has confirmed active China-linked nation-state exploitation of the closely related SharePoint ToolShell vulnerability chain, which has hit roughly 400 organizations including U.S. federal agencies. Do: Apply Microsoft's SharePoint Server security updates that ship this fix as soon as possible, prioritizing internet-facing servers, and treat this as urgent because it was patched alongside the actively exploited ToolShell chain. While patching, review authentication and web-server logs on SharePoint hosts for unexpected successful logons or anomalous requests that could indicate spoofing or compromise, and restrict network access to SharePoint (VPN, firewall rules, segmentation) if patching must be delayed. | 6.5 | 100% |
| largeTens of thousands of internet-facing SharePoint Server deployments, with a total on-prem installed base plausibly in the hundreds of thousands (estimate) |
Full article856 words · extracted from thehackernews.com · click to collapse
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 allows an authorized attacker to perform spoofing over a network," Microsoft said in an advisory released on July 20, 2025.
Microsoft also noted that CVE-2025-53770 and CVE-2025-53771 are related to two other SharePoint vulnerabilities documented by CVE-2025-49704 and CVE-2025-49706, which could be chained to achieve remote code execution. The exploit chain, referred to as ToolShell, was patched as part of the company's July 2025 Patch Tuesday update.
"The update for CVE-2025-53770 includes more robust protections than the update for CVE-2025-49704," the Windows maker said. "The update for CVE-2025-53771 includes more robust protections than the update for CVE-2025-49706."
It's worth noting that Microsoft previously characterized CVE-2025-53770 as a variant of CVE-2025-49706. When reached for comment about this discrepancy, a Microsoft spokesperson told The Hacker News that "it is prioritizing getting updates out to customers while also correcting any content inaccuracies as necessary."
The company also said that the current published content is correct and that the previous inconsistency does not impact the company's guidance for customers.
Both the identified flaws apply to on-premises SharePoint Servers only, and do not impact SharePoint Online in Microsoft 365. The issues have been addressed in the versions below (for now) -
- Microsoft SharePoint Server 2019 (16.0.10417.20027)
- Microsoft SharePoint Enterprise Server 2016 (16.0.5508.1000)
- Microsoft SharePoint Server Subscription Edition
- Microsoft SharePoint Server 2019 Core
- Microsoft SharePoint Server 2019 Language Pack
- Microsoft SharePoint Enterprise Server 2016
- Microsoft SharePoint Enterprise Server 2016 Language Pack
To mitigate potential attacks, customers are recommended to -
- Use supported versions of on-premises SharePoint Server (SharePoint Server 2016, 2019, and SharePoint Subscription Edition)
- Apply the latest security updates
- Ensure the Antimalware Scan Interface (AMSI) is turned on and enable Full Mode for optimal protection, along with an appropriate antivirus solution such as Defender Antivirus
- Deploy Microsoft Defender for Endpoint protection, or equivalent threat solutions
- Rotate SharePoint Server ASP.NET machine keys
"After applying the latest security updates above or enabling AMSI, it is critical that customers rotate SharePoint server ASP.NET machine keys and restart IIS on all SharePoint servers," Microsoft said. "If you cannot enable AMSI, you will need to rotate your keys after you install the new security update."
The development comes as Eye Security told The Hacker News that at least 54 organizations have been compromised, including banks, universities, and government entities. Active exploitation is said to have commenced around July 18, according to the company.
The U.S. Cybersecurity and Infrastructure Security Agency (CISA), for its part, added CVE-2025-53770 to its Known Exploited Vulnerabilities (KEV) catalog, requiring Federal Civilian Executive Branch (FCEB) agencies to apply the fixes by July 21, 2025.
Palo Alto Networks Unit 42, which is also tracking what it described as a "high-impact, ongoing threat campaign," said government, schools, healthcare, including hospitals, and large enterprise companies are at immediate risk.
"Attackers are bypassing identity controls, including MFA and SSO, to gain privileged access," Michael Sikorski, CTO and Head of Threat Intelligence for Unit 42 at Palo Alto Networks, told The Hacker News. "Once inside, they're exfiltrating sensitive data, deploying persistent backdoors, and stealing cryptographic keys. The attackers have leveraged this vulnerability to get into systems and are already establishing their foothold.
"If you have SharePoint on-prem exposed to the internet, you should assume that you have been compromised at this point. Patching alone is insufficient to fully evict the threat. What makes this especially concerning is SharePoint's deep integration with Microsoft's platform, including their services like Office, Teams, OneDrive and Outlook, which have all the information valuable to an attacker. A compromise doesn't stay contained—it opens the door to the entire network."
The cybersecurity vendor has also classified it as a high-severity, high-urgency threat, urging organizations running on-premises Microsoft SharePoint servers to apply the necessary patches with immediate effect, rotate all cryptographic material, and engage in incident response efforts.
"An immediate, band-aid fix would be to unplug your Microsoft SharePoint from the internet until a patch is available," Sikorski added. "A false sense of security could result in prolonged exposure and widespread compromise."
(The story was updated after publication on July 22, 2025, to include details of the latest fixes and change the CVSS score of CVE-2025-53771 from 6.3 to 7.1 based on Microsoft's advisory.)
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