CVE-2021-26421

Skype for Business and Lync Spoofing Vulnerability

CVSS 6.5 · Medium

External lookup

Potential internet exposure

Potential exposure only — not proof of vulnerability.Shodan results indicate potentially internet-exposed products, not confirmed vulnerable systems. They do not confirm that any returned system is vulnerable to CVE-2021-26421.

Product-level CPE searches intentionally omit version fields and NVD version-range or configuration certainty. Verify the exact product version and configuration independently.

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Product CPE queries

Derived from this CVE's existing NVD CPE 2.3 records; the application, operating-system, or hardware part is retained.

cpe:2.3:a:microsoft:lync_serverSearch this product on Shodan
cpe:2.3:a:microsoft:skype_for_business_serverSearch this product on Shodan

Exact CVE query

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vuln:CVE-2021-26421Search this CVE on Shodan

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Metadata

Canonical fields

NVD status

Unavailable

Published

May 11, 2021

Modified

Jun 17, 2026

Official record

Authoritative NVD record

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N

CWE IDs

Unavailable

Vendor classifications

How this vector reads

CVSS 3.1 base metrics decoded below. This explanation does not recalculate or change the NVD score.

Attack Vector (AV): Network. The vulnerable system can be reached across network boundaries.
Attack Complexity (AC): High. Successful exploitation depends on conditions outside the attacker's control.
Privileges Required (PR): Low. The attacker needs basic user-level privileges.
User Interaction (UI): Required. Another user must take an action for exploitation to succeed.
Scope (S): Changed. Impacts can cross into a different security authority.
Confidentiality Impact (C): High. There is a total or serious impact to this security property.
Integrity Impact (I): Low. There is a limited impact to this security property.
Availability Impact (A): None. There is no direct impact to this security property.

Signals

Exploitation indicators

0 stored signals · no KEV · 0 OTX pulses