Cyber Resilience

CVE-2023-41763

SSRF in Microsoft Skype For Business Server 2015 … 2019

CISA KEVActive ExploitationEUVD ExploitedSSRF
Published
10 October 2023
Modified
28 October 2025
KEV Added
10 October 2023
Patch / advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.90 99.8th percentile
Risk Priority 75 floored blend · peak EPSS

Summary

CVE-2023-41763 is a medium-severity SSRF (CWE-918) vulnerability in Microsoft Skype For Business Server. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities 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-2023-41763 is an elevation-of-privilege vulnerability in Skype for Business that stems from a server-side request forgery flaw (CWE-918). The affected component allows an unauthenticated network attacker to cause the server to issue requests to arbitrary destinations, resulting in limited information disclosure as reflected in its CVSS 5.3 score (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

An attacker with no credentials or user interaction can send crafted requests over the network to a Skype for Business server and obtain partial confidential data that would otherwise be inaccessible. Because the vulnerability requires no authentication and has a low attack complexity, it can be exploited from anywhere on the network reachable by the service.

Microsoft’s security update guide and the CISA Known Exploited Vulnerabilities catalog both reference the issue, indicating that administrators should apply the patches supplied through the standard Microsoft Update channels to eliminate the SSRF vector.

The EPSS score for this CVE rose sharply from a low baseline after disclosure, reaching a peak of 0.7335 on 2024-11-11 before receding to its current value of 0.1650; its inclusion in the CISA KEV catalog further confirms observed in-the-wild exploitation activity.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Skype for Business Elevation of Privilege Vulnerability

CWE(s)
KEV Date Added
10 October 2023

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2021-26855Same vendor: Microsoftboth on KEV
CVE-2022-41040Same vendor: Microsoftboth on KEV
CVE-2021-34473Same vendor: Microsoftboth on KEV
CVE-2026-55051Same vendor: Microsoft
CVE-2025-29972Same vendor: Microsoft
CVE-2025-21177Same vendor: Microsoft
CVE-2026-26120Same vendor: Microsoft
CVE-2026-21512Same vendor: Microsoft
CVE-2026-45502Same vendor: Microsoft
CVE-2026-26139Same vendor: Microsoft

Affected Assets

microsoft
skype for business server
2015, 2019

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)

Validate
Prove the fix (OWASP ASVS)
  • V1.3.6
  • V1.5.3
  • V5.3.2
  • V10.4.7

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.

addresses: CWE-918

Penetration testing attempts server-side requests to internal resources, identifying SSRF weaknesses for remediation.

addresses: CWE-918

Outbound connections to external resources can be monitored and limited at the boundary, reducing SSRF impact.

addresses: CWE-918

Validates server-side URLs and resource references to block SSRF attempts.

addresses: CWE-918

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.

PR.PS-06 mostly match
prevents

Secure development practices directly include input validation and destination allow-listing that prevent SSRF.

DE.CM-09 partial match
prevents

Runtime monitoring of web applications and services can detect anomalous outbound requests indicative of SSRF.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover and record SSRF flaws in web applications.

PR.IR-01 partial match
prevents

Network segmentation and egress controls can limit the damage from successful SSRF requests.

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.

prevents

Operational threat data describing SSRF campaigns can be used to tighten outbound-request allow-lists and detection rules before attackers exploit them.

References