EUVD-2026-73939
GHSA-935c-p9xv-m74w
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Adjacent-network position required but no credentials or interaction needed; successful spoofing yields full confidentiality and integrity impact; A:L reflects potential disruption, not denial.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
4DescriptionCVE.org
Improper verification of cryptographic signature in Skype for Business allows an unauthorized attacker to perform spoofing over an adjacent network.
AnalysisAI
Skype for Business Server's failure to properly verify cryptographic signatures (CWE-347) enables unauthenticated attackers on the same network segment to spoof identities or server endpoints, achieving high confidentiality and integrity impact across three distinct server release lines. All on-premises deployments of SfB Server 2015 CU13, 2019 CU8, and Subscription Edition CU1 below specific cumulative-update thresholds are confirmed affected, with patched releases available from Microsoft. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires network adjacency: the attacker must reside on the same network segment, subnet, or VLAN as the Skype for Business Server at the time of the attack, consistent with the CVSS AV:A metric. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 8.3 score reflects a genuine and serious threat: adjacent-network, unauthenticated access requiring no user interaction, with high confidentiality and integrity impact and only low availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply vendor-released cumulative update patches immediately: Skype for Business Server 2019 CU8 should be updated to build 7.0.2046.569 or later; Skype for Business Server Subscription Edition CU1 should be updated to build 7.0.2046.879 or later; and Skype for Business Server 2015 CU13 should be updated to build 6.0.9319.885 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all on-premises Skype for Business Server deployments and document which versions are running (2015, 2019, or Subscription Edition) and their current cumulative update levels to determine vulnerability status; assess network segmentation and access controls protecting affected systems. …
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External POC / Exploit Code
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