Microsoft SharePoint Enterprise Server 2016/2019/Subscription Edition HTTP Header /_layouts/SignOut.aspx Referer ToolShell deserialization

CVSS Meta Temp Score
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CTI Interest Score
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9.6$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Microsoft SharePoint Enterprise Server 2016/2019/Subscription Edition. Affected by this vulnerability is an unknown functionality of the file /_layouts/SignOut.aspx of the component HTTP Header Handler. Performing a manipulation of the argument Referer results in deserialization. This vulnerability is identified as CVE-2025-53770. The attack can be initiated remotely. Additionally, an exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Microsoft SharePoint Enterprise Server 2016/2019/Subscription Edition. It has been classified as very critical. This affects an unknown functionality of the file /_layouts/SignOut.aspx of the component HTTP Header Handler. The manipulation of the argument Referer with an unknown input leads to a deserialization vulnerability. CWE is classifying the issue as CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.

It is possible to read the advisory at msrc.microsoft.com. This vulnerability is uniquely identified as CVE-2025-53770 since 07/09/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details and a public exploit are known. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/15/2025).

The exploit is shared for download at exploit-db.com. It is declared as attacked. We expect the 0-day to have been worth approximately . By approaching the search of inurl:_layouts/SignOut.aspx it is possible to find vulnerable targets with Google Hacking. The vulnerability scanner Nessus provides a plugin with the ID 242415 (Security Updates for Microsoft SharePoint Server Subscription Edition (July 2025)), which helps to determine the existence of the flaw in a target environment. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 07/20/2025 with a due date of 07/21/2025:

Disconnect public-facing versions of SharePoint Server that have reached their end-of-life (EOL) or end-of-service (EOS) to include SharePoint Server 2013 and earlier versions. For supported versions, please follow the mitigations according to CISA (URL l

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Exploit-DB (52405), Zero-Day.cz (1017), Tenable (242415), EUVD (EUVD-2025-21981) and CERT Bund (WID-SEC-2025-1598). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Microsoft SharePoint Server 2019
  • Microsoft SharePoint
  • Microsoft SharePoint Server 2016

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.8
VulDB Meta Temp Score: 9.6

VulDB Base Score: 9.8
VulDB Temp Score: 9.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 9.8
CNA Vector (microsoft): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Deserialization
CWE: CWE-502 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Access: Public
Status: Attacked
Download: 🔒
Google Hack: 🔒

EPSS Score: 🔒
EPSS Percentile: 🔒

KEV Added: 🔒
KEV Due: 🔒
KEV Remediation: 🔒
KEV Ransomware: 🔒
KEV Notice: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 242415
Nessus Name: Security Updates for Microsoft SharePoint Server Subscription Edition (July 2025)

Exploit-DB: 🔒
Zero-Day.cz: 🔒

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

07/09/2025 CVE reserved
07/20/2025 +11 days Advisory disclosed
07/20/2025 +0 days VulDB entry created
08/15/2025 +26 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2025-53770 (🔒)
GCVE (CVE): GCVE-0-2025-53770
GCVE (VulDB): GCVE-100-317031
EUVD: 🔒
CERT Bund: WID-SEC-2025-1598 - Microsoft SharePoint (On-premises): Mehrere Schwachstellen

scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 07/20/2025 11:39
Updated: 08/15/2025 23:48
Changes: 07/20/2025 11:39 (63), 07/20/2025 14:20 (1), 07/21/2025 01:57 (11), 07/21/2025 12:15 (2), 07/21/2025 16:12 (1), 07/21/2025 16:24 (6), 07/21/2025 23:14 (6), 07/22/2025 18:08 (1), 07/25/2025 21:02 (2), 07/29/2025 19:12 (2), 08/04/2025 16:32 (1), 08/15/2025 23:48 (3)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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