Skype for Business
CVE-2026-66303 — Skype for Business and Lync Denial of Service Vulnerability
Executive Summary
Null pointer dereference in Skype for Business allows an authorized attacker to deny service over a network.
Overview
6.5
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
Low
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
None
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 5.7
EPSS Score
No EPSS score available for this CVE.
View on FIRST.orgAffected Products
3 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Skype for Business Server 2015 CU13 | 5123301 (Security Update) |
Important | Denial of Service | Maybe |
| Skype for Business Server 2019 CU8 | 5123300 (Security Update) |
Important | Denial of Service | Maybe |
| Skype for Business Server Subscription Edition CU1 | 5123287 (Security Update) |
Important | Denial of Service | Maybe |
Patches
3 patches
| Article | Type | Restart |
|---|---|---|
5123301 |
Security Update | Maybe |
5123300 |
Security Update | Maybe |
5123287 |
Security Update | Maybe |
Exploits & PoC
No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.
Detection Rules
No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.
Acknowledgments
Manish Kumar
Pranjal Varshney
References
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