CVE-2026-66307: microsoft skype_for_business_server Integer Underflow (Wrap or Wraparound)
CVSS: 7.5v3.1HighAnalyzed
Published 08-09-2026Last modified 14-10-2026
Vulnerability summary
CVE-2026-66307 is a high (CVSS 7.5) Integer Underflow (Wrap or Wraparound) vulnerability in microsoft skype_for_business_server. EPSS estimates a 1.17% chance of exploitation in the next 30 days, higher than 67% of scored vulnerabilities.
CVSS score
7.5/10
010
High · v3.1 (CVE.org)EPSS score
1.17%
0%100%
Low · +0.54 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 08-09-2026PublishedVulnerability first disclosed.
- 14-10-2026Last modifiedVulnerability information updated.
Description
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
CVSS metrics
2 scores · 2 sources · 1 versionHigh 7.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:CSourcesAll 2 agree
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.17%
Chance of exploitation in the next 30 days
Percentile
67%
Versus all other CVEs
30-day change
+0.54 pp
From 0.63% on 20-09-2026
20-09-202620-10-2026
EPSS score1.17%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Microsoft5 products
- skype_for_business_server2015:cumulative_update_13 | 2015:cumulative_update_13_hotfix_2 | 2019:cumulative_update_8 | 2019:cumulative_update_8_hotfix1 | 2019:cumulative_update_8_hotfix2
- skype for business server 2015 cu13≥ 9319.0, < 6.0.9319.885
- skype for business server 2019 cu8≥ 2046.0, < 7.0.2046.569
- skype_for_business_server_subscription_edition7.0.2046.849
- skype for business server subscription edition cu1≥ 2046.0, < 7.0.2046.879
1 vendor · 5 products
