CVE-2025-53771VulnerabilityPublished 20 Jul 2025Updated 13 Feb 2026

CVE-2025-53771: Microsoft SharePoint Enterprise Server 2016 · Improper Authentication

Affects Microsoft SharePoint Enterprise Server 2016Source CVE Database V5

Not known to be exploited · public exploit available (Metasploit) · 99% EPSS · CVSS 6.5 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 99.8% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Base metrics

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

Temporal metrics

Exploit Code Maturity: Proof-of-Concept
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.
Exploit Code Maturity: Proof-of-Concept: Proof-of-concept exploit code is available, or an attack demonstration is not practical for most systems. The code or technique is not functional in all situations and may require substantial modification by a skilled attacker.
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

Disclosed: evidence found.
CVE published 20 Jul 2025
Detectable: evidence found.
nuclei template: Microsoft SharePoint Server - Authentication Bypass (ToolShell)
Weaponised: evidence found.
1 Metasploit module
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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.

What to do

Affected software

Product	Affected	Fixed in
Microsoft Microsoft SharePoint Enterprise Server 2016	Affected =16.0.0	Fixed in–

AI-suggested

Until an official patch is released, European organizations should implement network-level mitigations such as restricting external access to SharePoint servers via firewalls and VPNs, and enforcing strict network segmentation to isolate SharePoint infrastructure from untrusted networks. Deploy intrusion detection and prevention systems (IDS/IPS) tuned to detect anomalous authentication or spoofing attempts targeting SharePoint. Enable and closely monitor detailed authentication and access logs within SharePoint to identify suspicious activities early. Consider implementing multi-factor authentication (MFA) for SharePoint access where possible to add an additional layer of security. Regularly review and minimize permissions assigned within SharePoint to reduce potential impact. Prepare incident response plans specific to SharePoint compromise scenarios and ensure timely application of official patches once available. Engage with Microsoft support channels for updates on patch releases and advisories.

Description

Improper authentication in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.

Impact

For European organizations, this vulnerability could lead to unauthorized access to confidential documents and collaboration data stored in SharePoint Enterprise Server 2016. The spoofing capability may allow attackers to impersonate legitimate users or services, undermining trust in authentication mechanisms and potentially enabling further lateral movement within networks. Sectors such as government, finance, healthcare, and critical infrastructure that rely heavily on SharePoint for internal communication and document sharing are at heightened risk. The medium severity indicates that while the vulnerability is serious, it does not directly impact system availability, reducing the likelihood of widespread denial-of-service conditions. However, the compromise of confidentiality and integrity could result in data breaches, regulatory non-compliance (e.g., GDPR), and reputational damage. The lack of required privileges or user interaction increases the risk of exploitation, especially in environments where SharePoint servers are exposed to untrusted networks or insufficiently segmented.

Metasploit modules

Microsoft SharePoint Server ToolPane Unauthenticated Remote Code Execution (aka ToolShell)exploit · Excellent (opens in a new tab)

Nuclei detection templates

Microsoft SharePoint Server - Authentication Bypass (ToolShell)medium (opens in a new tab)

Public tooling indexed from Metasploit Framework, Exploit-DB and ProjectDiscovery nuclei-templates. Its existence raises the odds of exploitation; it does not confirm attacks.

CWE-287Improper Authentication (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Libraries or Frameworks
Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
V9.2.3 (opens in a new tab)
Attack patterns
Fake the Source of Data (opens in a new tab)
Utilizing REST's Trust in the System Resource to Obtain Sensitive Data (opens in a new tab)
Session Hijacking (opens in a new tab)
Token Impersonation (opens in a new tab)
Upload a Web Shell to a Web Server (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Feb 2026, 10:33 UTC

Public exploits and detection1 Metasploit module, a Nuclei detection template

WeaknessesCWE-287

Technical details

References

Community reviews

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