Credential disclosure via calendar-sharing URL retrieval
Published Dec 12, 2023 · Updated Jan 1, 2025
Information disclosure in Microsoft Outlook for affected Office releases allows remote attackers to obtain Net-NTLMv2 responses via email. Crafted Content-Class and x-sharing-config-url headers make Outlook retrieve an attacker-controlled calendar path and authenticate to it. A recipient must click the calendar-sharing prompt; the captured response supports offline password guessing or authentication relay.
Summary
What happened
Information disclosure in Microsoft Outlook for affected Office releases allows remote attackers to obtain Net-NTLMv2 responses via email. Crafted Content-Class and x-sharing-config-url headers make Outlook retrieve an attacker-controlled calendar path and authenticate to it. A recipient must click the calendar-sharing prompt; the captured response supports offline password guessing or authentication relay.
The record
- CVE
- CVE-2023-35636
- Published
- Dec 12, 2023
- Updated
- Jan 1, 2025
- Vendor
- Microsoft
- Product
- Microsoft Office 2016
- Classifications
- CWE-200, T1187
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 12, 2023CVE publishedPublication date reported by the CVE source.
- Jan 1, 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=16.0.0 <16.0.5426.1000
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Varonis calendar-sharing header demonstrationfunctional · demonstrated
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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