CVE-2023-21761
SSRF in Microsoft Exchange Server 2016 … 2019
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2023-21761 is a high-severity SSRF (CWE-918) vulnerability in Microsoft Exchange Server. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique LSASS Memory (T1003.001); ranked in the top 25% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2023-21761 is an information disclosure vulnerability in Microsoft Exchange Server, assigned a CVSS 3.1 base score of 7.5. The flaw is reachable over the network without authentication or user interaction and results in high confidentiality impact while leaving integrity and availability unaffected. It is tracked under CWE-918, indicating a server-side request forgery class issue.
An unauthenticated attacker can send crafted requests to an affected Exchange Server and obtain sensitive information that would otherwise be inaccessible. Because the attack requires no credentials and can be performed remotely, the vulnerability is exploitable by any party able to reach the server on the network.
Microsoft has published an advisory for CVE-2023-21761 that directs administrators to the corresponding security update. The EPSS score for this CVE has remained flat at 0.1307 since disclosure, indicating no material increase in observed exploitation interest.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-25928
Vulnerability Data
Microsoft Exchange Server Information Disclosure Vulnerability
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.6V1.5.3V5.3.2V10.4.7
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Penetration testing attempts server-side requests to internal resources, identifying SSRF weaknesses for remediation.
Outbound connections to external resources can be monitored and limited at the boundary, reducing SSRF impact.
Validates server-side URLs and resource references to block SSRF attempts.
Detects server-side request forgery through monitoring of unexpected outbound connections.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Runtime monitoring of web applications and services can detect anomalous outbound requests indicative of SSRF.
Vulnerability identification processes can discover and record SSRF flaws in web applications.
Network segmentation and egress controls can limit the damage from successful SSRF requests.
Secure development practices directly include input validation and destination allow-listing that prevent SSRF.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.