Background exploitation KEV catalog No authentication
CVE-2023-41763

Microsoft Skype for Business Privilege Escalation Vulnerability

Skype for Business Elevation of Privilege Vulnerability

CheckOps priority index
7.2/10 Patch within 7 days
Severity5.3
Probability9.0
Exploitation4/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 90.3% −0.3 pts in 7 days
CVSS 3.1 5.3 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:
Exploited for 1,120 days 10 Oct 2023
CISA due date 31 Oct 2023 for US federal agencies

Exploitation probability EPSS · FIRST

05010026 Sep05 Oct15 Oct24 Oct02 Nov
EPSS probability (%)Percentile among all CVEs

Exploitation signals 4 / 5

  • KEV catalog (CISA)10 Oct 2023
  • Exploited in EUVD (ENISA)10 Oct 2023
  • Used by ransomwareno
  • EPSS above 10 %90.3%
  • No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Affected products

Skype for Business Server 2015 CU13Skype for Business Server 2019 CU7Skype for Business
Affected versions
  • 9319.0 <6.0.9319.869
  • 2046.0 <7.0.246.530
Weaknesses (CWE)

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

  1. Published

  2. Exploitation reported (ENISA)

  3. Added to the KEV catalog

  4. CISA remediation due date

  5. EPSS peak: 90.9%

References

Other exploited vulnerabilities from the same vendor

  • CVE-2026-96951Microsoft Windows Command Injection Vulnerability
    5.6 · Actively exploited
  • CVE-2026-65660Microsoft SharePoint Code Injection Vulnerability
    5.0 · Actively exploited
  • CVE-2026-85880Microsoft Windows Heap-Based Buffer Overflow Vulnerability
    4.3 · Actively exploited
  • CVE-2026-81963Microsoft Windows Link Following Vulnerability
    4.3 · Actively exploited
  • CVE-2019-1068Microsoft SQL Server Remote Code Execution Vulnerability
    7.0 · Actively exploited
  • CVE-2026-69836Microsoft Entra
    5.3 · Actively exploited

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Sources: CISA KEV · ENISA EUVD · FIRST EPSS · OSV. Public data aggregated by CheckOps, updated automatically. Source texts remain the property of their authors. All exploited vulnerabilities