Report · SecurityWeekAbout CVE-2026-20963Published 19 Mar 2026

CISA Warns of Attacks Exploiting Recent SharePoint Vulnerability

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Authoritative record:CVE-2026-20963· Critical 9.8

Exploited in the wild · KEV due 21 Mar 2026 : upgrade to 16.0.5535.1001 now.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

9.8Critical

How severe the flaw is on the 0–10 CVSS scale.

KEV deadline: 21 Mar 2026 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
Patch: Available – fixed in 16.0.5535.1001, 16.0.10417.20083, 16.0.19127.20442

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Base metrics

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Temporal metrics

Exploit Code Maturity: Unproven
Remediation Level: Official Fix
Report Confidence: Confirmed

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Exploit Code Maturity: Unproven: No exploit code is available, or an exploit is theoretical.
Remediation Level: Official Fix: A complete vendor solution is available. Either the vendor has issued an official patch, or an upgrade is available.
Report Confidence: Confirmed: Detailed reports exist, or functional reproduction is possible (functional exploits may provide this). Source code is available to independently verify the assertions of the research, or the author or vendor of the affected code has confirmed the presence of the vulnerability.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 13 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 64 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE ID reserved
by Microsoft Corporation
4 Dec 202520:04 UTC, 40 days before disclosure
CVE published
on cve.org
13 Jan 202617:56 UTC, t = 0
In Threat Radar
record ingested
13 Jan 202618:11 UTC, 15 minutes after disclosure
Added to CISA KEV (opens in a new tab)
exploitation confirmed
18 Mar 2026, 64 days after disclosure
KEV remediation due
US federal deadline
21 Mar 2026, 67 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

remote

What to do

Upgrade Microsoft SharePoint to 16.0.5535.1001 (Enterprise Server 2016) or 16.0.10417.20083 (Server 2019) or 16.0.19127.20442 (Server Subscription Edition).

Affected software

Product	Affected	Fixed in
MicrosoftMicrosoft SharePoint Enterprise Server 2016	Affected >=16.0.0 <16.0.5535.1001	Fixed in 16.0.5535.1001
MicrosoftMicrosoft SharePoint Server 2019	Affected >=16.0.0 <16.0.10417.20083	Fixed in 16.0.10417.20083
MicrosoftMicrosoft SharePoint Server Subscription Edition	Affected >=16.0.0 <16.0.19127.20442	Fixed in 16.0.19127.20442

AI-suggested

To mitigate this threat effectively, organizations should: 1) Immediately verify and apply the Microsoft patch for CVE-2026-20963 on all SharePoint servers, prioritizing internet-facing and critical systems. 2) Conduct thorough vulnerability assessments and penetration tests to identify unpatched or misconfigured SharePoint instances. 3) Implement strict network segmentation to isolate SharePoint servers from sensitive internal resources and limit lateral movement. 4) Enable and monitor detailed logging on SharePoint and associated infrastructure to detect anomalous activities indicative of exploitation attempts. 5) Deploy web application firewalls (WAFs) with updated signatures to block known attack patterns targeting this vulnerability. 6) Educate IT and security teams on the indicators of compromise related to SharePoint exploitation and establish incident response plans. 7) Restrict administrative access to SharePoint servers using multi-factor authentication and least privilege principles. 8) Regularly review and update security configurations and ensure backup and recovery processes are tested and reliable.

Description

CISA has issued a warning about active exploitation of a recently patched critical remote code execution vulnerability in Microsoft SharePoint, identified as CVE-2026-20963. This vulnerability allows attackers to execute arbitrary code remotely on vulnerable SharePoint servers without authentication, potentially leading to full system compromise. Although Microsoft released a patch in January, attackers have begun exploiting unpatched systems in the wild. The vulnerability affects SharePoint installations globally, posing significant risks to organizations relying on this platform for collaboration and document management. Exploitation can result in data breaches, disruption of services, and lateral movement within networks. Immediate patching and enhanced monitoring are critical to mitigate this threat. Countries with widespread SharePoint deployments and high-value targets are at elevated risk. Given the ease of exploitation and potential impact, the severity is assessed as critical.

Impact

The exploitation of CVE-2026-20963 can have severe consequences for organizations worldwide. Attackers gaining remote code execution on SharePoint servers can compromise sensitive corporate data, intellectual property, and user credentials stored or managed through SharePoint. This can lead to data breaches, regulatory non-compliance, and reputational damage. Additionally, attackers can use compromised SharePoint servers as footholds to move laterally within corporate networks, escalating privileges and targeting other critical infrastructure. Disruption of SharePoint services can also impact business continuity, affecting collaboration and productivity. Given SharePoint's prevalence in government, financial, healthcare, and enterprise sectors, the threat poses a broad risk landscape. Organizations that delay patching or lack robust detection capabilities are particularly vulnerable to targeted attacks and potential ransomware deployment following initial compromise.

Summary

The security threat centers on CVE-2026-20963, a critical remote code execution vulnerability in Microsoft SharePoint. This flaw enables attackers to remotely execute arbitrary code on affected SharePoint servers without requiring authentication or user interaction. Microsoft addressed this vulnerability with a patch released in January 2026; however, threat actors have started exploiting unpatched systems in the wild, as warned by CISA. The vulnerability likely stems from improper input validation or deserialization issues within SharePoint's web services, allowing attackers to inject and execute malicious payloads remotely. Successful exploitation can grant attackers full control over the SharePoint server, enabling data theft, deployment of malware, and pivoting to other network assets. SharePoint is widely used in enterprise environments for collaboration and document management, making this vulnerability particularly impactful. The lack of known exploit samples or detailed indicators suggests early-stage exploitation, but the critical nature demands urgent attention. Organizations running SharePoint should verify patch status, monitor for suspicious activity, and apply additional network segmentation and access controls to limit exposure.

References

securityweek.com/cisa-warns-of-attacks-exploiting-recent-sharepoint-vulnerability/ (opens in a new tab)

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Description

AI analysisMachine-generated, updated 19 Mar 2026, 09:53 UTC

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