Authenticated service interruption via validator regex backtracking
Published Apr 13, 2021 · Updated Aug 3, 2024
Regular expression denial of service in Microsoft SharePoint Server 2010 through 2019 allows remote authenticated users to interrupt service. The InputFormRegularExpressionValidator class accepts a user-controlled ValidationExpression without adequate validation, enabling catastrophic backtracking during regular-expression evaluation. An authenticated SharePoint account is required, and the documented consequence is availability loss rather than data disclosure or modification.
Summary
What happened
Regular expression denial of service in Microsoft SharePoint Server 2010 through 2019 allows remote authenticated users to interrupt service. The InputFormRegularExpressionValidator class accepts a user-controlled ValidationExpression without adequate validation, enabling catastrophic backtracking during regular-expression evaluation. An authenticated SharePoint account is required, and the documented consequence is availability loss rather than data disclosure or modification.
The record
- CVE
- CVE-2021-28450
- Published
- Apr 13, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Microsoft SharePoint Enterprise Server 2016
- Classifications
- T1499.003
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 13, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 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?
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- Affected versionversion=16.0.0 <publication
What conditions does exploitation require?
What is affected?
Published CVSS scores
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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.
Weakness, pattern, technique
Public exploit references
- InputFormRegularExpressionValidator ReDoS demonstrationproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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