CVE-2020-1025Network attack vector

Authentication bypass via modified OAuth token

Published Jul 14, 2020 · Updated Aug 4, 2024

OAuth token validation flaws in Microsoft SharePoint and Skype for Business servers allow remote attackers to bypass authentication. The server-side OAuth validation path accepts an attacker-modified token without correctly validating it, so the token is treated as authorized. No credentials or user interaction are required; successful requests gain improper access to protected server resources.

CVSS severity9.8
Critical
EPSS probability5.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OAuth token validation flaws in Microsoft SharePoint and Skype for Business servers allow remote attackers to bypass authentication. The server-side OAuth validation path accepts an attacker-modified token without correctly validating it, so the token is treated as authorized. No credentials or user interaction are required; successful requests gain improper access to protected server resources.

The record

CVE
CVE-2020-1025
Published
Jul 14, 2020
Updated
Aug 4, 2024
Vendor
Microsoft
Product
Microsoft SharePoint Enterprise Server 2016
Classifications
CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=16.0.0 <publication

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <publication
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <publication
Microsoft · Skype for Business Serverversion=2015 CU 8 <publication; version=7.0.0 <publication
Microsoft · Microsoft SharePoint Foundationversion=15.0.0 <publication
Microsoft · Microsoft Lync Serverversion=0 <publication

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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