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SharePoint Enterprise Server 2016

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2026-009: Critical Vulnerabilities in Microsoft SharePoint

WatchTowr observed active exploitation of SharePoint RCE CVE-2026-50522 (CVSS 9.8), part of an ongoing wave of exploited on-prem SharePoint flaws patched by Microsoft.

On 14 July 2026 Microsoft released updates for critical SharePoint Server RCE flaws, including CVE-2026-50522 (CVSS 9.8), a deserialisation vulnerability possibly exploitable without authentication. On 20 July 2026 WatchTowr published PoC exploit code and observed active exploitation of CVE-2026-50522, prompting CISA to urge SharePoint hardening. The advisory also covers recently fixed SharePoint flaws: CVE-2026-32201 (6.5, spoofing), CVE-2026-45659 (8.8, authenticated RCE), CVE-2026-56164 (9.8, unauthenticated privilege escalation), and CVE-2026-58644 (9.8, unauthenticated RCE). Affected products include SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016; CERT-EU recommends immediate patching, credential rotation, and compromise assessments.

CERT-EU Advisoriesupdated · 8d agofirst · Jul 22, 2026Exploit / PoC in the wild 3 sourcesCVE-2026-50522CVE-2026-32201CVE-2026-45659+2 CVEs

2026-004: Critical Vulnerability in SharePoint Exploited

CVE-2026-20963 (CVSS 9.8), an unauthenticated RCE in on-prem SharePoint, was added to CISA's KEV on 18 March 2026 and is actively exploited.

CERT-EU warns about CVE-2026-20963, a CVSS 9.8 unauthenticated remote code execution flaw in SharePoint caused by deserialisation of untrusted data, affecting SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016. Microsoft raised the CVSS score on 17 March 2026 and the flaw entered CISA's Known Exploited Vulnerabilities catalogue on 18 March 2026. Three additional SharePoint RCE flaws (CVE-2026-26106, CVE-2026-26113, CVE-2026-26114) were fixed in the March 2026 release. CERT-EU urges immediate patching of internet-facing servers plus AMSI Full Mode, EDR deployment, ASP.NET machine key rotation, and compromise assessments.

CERT-EU Advisoriesupdated · 8d agofirst · Mar 25, 2026Exploit / PoC in the wild 3 sourcesCVE-2026-20963CVE-2026-26106CVE-2026-26113+1 CVEs

Related CVEs

  • Deserialization RCE in Microsoft SharePoint Exploited in the Wild
    CVE-2026-20963 is a deserialization of untrusted data flaw (CWE-502) in Microsoft SharePoint that allows an unauthorized attacker to execute code remotely over the network. The flaw is triggered when SharePoint processes maliciously crafted serialized data without validating it, enabling an attacker to run arbitrary code in the context of the SharePoint service. Successful exploitation gives the attacker code execution on the affected SharePoint server, a foothold that typically supports further lateral movement and data access within the environment. Organizations running affected SharePoint deployments are in scope, though affected version ranges have not yet been published in the available data. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2026-03-18, confirming active exploitation, and its EPSS of 31.6% (98th percentile) indicates a high near-term probability of exploitation; no public proof-of-concept is known and CVSS scoring is not yet available.
    · Microsoft SharePoint KEVmass
  • Missing Authentication in Microsoft SharePoint Server Allows Privilege Escalation
    Microsoft SharePoint Server contains a missing authentication for critical function vulnerability (CWE-306) that lets an unauthenticated attacker elevate privileges over a network without valid credentials. The flaw is triggered when the affected SharePoint function is accessed remotely without any authentication check, allowing an attacker to gain higher privileges than intended. Successful exploitation could enable an attacker to take elevated actions within the SharePoint environment, potentially leading to further compromise of the server and its data. All organizations running on-premises Microsoft SharePoint Server are potentially affected, though specific versions have not yet been enumerated by Microsoft or CISA. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2026-07-14, indicating it is being actively exploited, and its EPSS score of 26.6% (98th percentile) reflects a high near-term exploitation risk.
    · Microsoft SharePoint Server KEVmass
  • Unauthenticated Deserialization RCE in Microsoft SharePoint Server
    CVE-2026-58644 is a critical (CVSS 9.8) deserialization-of-untrusted-data flaw (CWE-502) in Microsoft SharePoint Server that allows an unauthorized attacker to execute code over a network. An attacker triggers it by sending crafted serialized data to the server, with no privileges or user interaction required, gaining code execution in the context of the SharePoint service. Any organization running on-premises SharePoint Server is affected, with highest risk for instances reachable from the internet or by untrusted network users. CISA added the flaw to its Known Exploited Vulnerabilities catalog on 2026-07-16, and contemporaneous headlines describe an exploited SharePoint zero-day, indicating active in-the-wild exploitation; EPSS assigns a roughly 16% probability of exploitation within 30 days (97th percentile). Fixes shipped in Microsoft's July 2026 Patch Tuesday release (621 CVEs total), while no public proof-of-concept for this specific CVE is documented.
    · Microsoft SharePoint Server (on-premises) KEVmass
  • Unauthenticated Deserialization RCE in Microsoft SharePoint Server
    CVE-2026-50522 is a deserialization of untrusted data flaw (CWE-502) in Microsoft SharePoint Server that allows an unauthenticated attacker to send maliciously crafted serialized data over the network and execute code on the server, reflected in its 9.8 critical CVSS score with no privileges or user interaction required. Successful exploitation yields full remote code execution with high impact on confidentiality, integrity, and availability, giving attackers a foothold for follow-on actions such as data theft, lateral movement, or ransomware. Any organization running on-premises SharePoint Server is in scope, particularly deployments reachable from untrusted networks; the required action notes stakeholders must evaluate each asset's internet exposure under CISA BOD 26-04. The flaw is under active exploitation: CISA added it to the Known Exploited Vulnerabilities catalog on 2026-07-22 and security news headlines describe it as a critical RCE exploited in the wild, with some reports referencing exploitation after a public proof-of-concept release and an authentication bypass. The structured record lists no public PoC as confirmed, but an EPSS of 84.6% (100th percentile) underscores a very high near-term exploitation likelihood.
    · Microsoft SharePoint Server (on-premises) KEVmass
  • Authenticated Deserialization RCE in Microsoft SharePoint Server (Actively Exploited)
    CVE-2026-45659 is a deserialization-of-untrusted-data vulnerability (CWE-502) in Microsoft SharePoint Server in which an authorized (authenticated, low-privilege) attacker can submit crafted serialized data over the network, with no user interaction required, to execute code on the server. Successful exploitation carries high impact on confidentiality, integrity, and availability within the SharePoint service context, giving attackers a foothold for follow-on activity, and CISA notes that ransomware use is known. Organizations running on-premises Microsoft SharePoint Server are affected; the source data lists no specific version ranges, and the CPE scope (sharepoint server) points to the on-premises product rather than the Microsoft-managed SharePoint Online service. The flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2026-07-01 after active exploitation, and its EPSS score of 76.1% (100th percentile) indicates a high probability of near-term exploitation. The CVE record lists no public proof-of-concept, though related reporting describes exploitation activity following a public PoC release for a SharePoint authentication bypass.
    · Microsoft SharePoint Server KEV ransomwaremass
  • Improper Input Validation Spoofing Vulnerability in Microsoft SharePoint Server
    Microsoft SharePoint Server contains an improper input validation flaw (CWE-20) that can be triggered by an unauthenticated, network-based attacker submitting crafted input to the server. Successful exploitation allows the attacker to perform spoofing over the network, impersonating a trusted user or source within SharePoint; detailed impact mechanics have not been published and no CVSS score or public proof-of-concept is available. Any organization running on-premises Microsoft SharePoint Server is potentially affected, and the available data does not specify affected version ranges. CISA added the vulnerability to the Known Exploited Vulnerabilities catalog on 2026-04-14, indicating evidence of active exploitation, and EPSS assigns a 42.8% probability of exploitation within 30 days (99th percentile). Ransomware association is currently unknown.
    · Microsoft SharePoint Server KEVmass
  • Improper input validation in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
    Improper input validation in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
    · microsoft sharepoint server
  • Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
    Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
    · microsoft sharepoint server
  • Untrusted pointer dereference in Microsoft Office allows an unauthorized attacker to execute code locally.
    Untrusted pointer dereference in Microsoft Office allows an unauthorized attacker to execute code locally.
    · microsoft 365 apps · microsoft office

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