Authenticated NTLM relay via unchecked UNC path
Published Nov 14, 2023 · Updated Oct 8, 2025
Improper input validation in affected Microsoft Exchange Server 2016 and 2019 builds allows remote authenticated users to relay NTLM credentials. The IsUNCPath method fails to validate an attacker-controlled path before Exchange accesses it, causing SYSTEM-context NTLM authentication to be relayed. A low-privileged Exchange account and adjacent-network access are required; successful exploitation lets the attacker reuse the relayed credentials for further access.
Summary
What happened
Improper input validation in affected Microsoft Exchange Server 2016 and 2019 builds allows remote authenticated users to relay NTLM credentials. The IsUNCPath method fails to validate an attacker-controlled path before Exchange accesses it, causing SYSTEM-context NTLM authentication to be relayed. A low-privileged Exchange account and adjacent-network access are required; successful exploitation lets the attacker reuse the relayed credentials for further access.
The record
- CVE
- CVE-2023-36035
- Published
- Nov 14, 2023
- Updated
- Oct 8, 2025
- Vendor
- Microsoft
- Product
- Microsoft Exchange Server 2019 Cumulative Update 12
- Classifications
- CWE-502, T1557
- Attack vector
- adjacent
- Privileges
- authenticated
Timeline
How it unfolded
- Nov 14, 2023CVE publishedPublication date reported by the CVE source.
- Oct 8, 2025Record 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.
- Affected versionversion=15.02.0 <15.02.1118.040
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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