How severe is CVE-2026-66306?

CVE-2026-66306 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-66306 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-66306?

CVE-2026-66306 primarily affects Microsoft Skype For Business Server. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-66306?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-66306 published?

CVE-2026-66306 was published on 2026-09-08 and last updated on 2026-09-16.

CVE-2026-66306

CVE-2026-66306 is a medium-severity vulnerability in Microsoft Skype For Business Server with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-209.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-209
Affected product: Microsoft Skype For Business Server
Published: 2026-09-08
Last modified: 2026-09-16

Description

Generation of error message containing sensitive information in Skype for Business allows an unauthorized attacker to disclose information over a network.

Frequently asked questions

What is CVE-2026-66306?: Generation of error message containing sensitive information in Skype for Business allows an unauthorized attacker to disclose information over a network.
How severe is CVE-2026-66306?: CVE-2026-66306 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-66306 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-66306?: CVE-2026-66306 primarily affects Microsoft Skype For Business Server. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-66306?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-66306 published?: CVE-2026-66306 was published on 2026-09-08 and last updated on 2026-09-16.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66306

Affected products (6)

cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_13:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_13_hotfix_2:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8_hotfix1:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8_hotfix2:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server_subscription_edition:7.0.2046.849:*:*:*:*:*:*:*

More vulnerabilities in Microsoft Skype For Business Server

CVE-2026-66302 — Critical (CVSS 9.8): External control of file name or path in Skype for Business allows an unauthorized attacker to execute code over a…
CVE-2026-69646 — High (CVSS 8.3): Improper verification of cryptographic signature in Skype for Business allows an unauthorized attacker to perform…
CVE-2026-66307 — High (CVSS 7.5): Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a…
CVE-2026-66304 — High (CVSS 7.5): Server-side request forgery (ssrf) in Skype for Business allows an unauthorized attacker to disclose information over a…
CVE-2023-36789 — High (CVSS 7.2): Skype for Business Remote Code Execution Vulnerability
CVE-2023-36786 — High (CVSS 7.2): Skype for Business Remote Code Execution Vulnerability

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