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CVE-2026-66303Skype for Business and Lync Denial of Service Vulnerability
- 6.5MediumCVSS base score
- 1.1%Exploitation in 30 daysEPSS · top 33% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Null pointer dereference in Skype for Business allows an authorized attacker to deny service over a network.
Timeline
ID reserved
By microsoft
- 46 days later
· 46 days later
Published
- 2 months later
· 2 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoftCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C |
| NVDNVD · Analyzed | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 1.1% · top 33% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
Microsoft · Skype for Business Server 2015 CU13
- affected 9319.0 – < 6.0.9319.885
Microsoft · Skype for Business Server 2019 CU8
- affected 2046.0 – < 7.0.2046.569
Microsoft · Skype for Business Server Subscription Edition CU1
- affected 2046.0 – < 7.0.2046.879
References
References1
- Skype for Business and Lync Denial of Service Vulnerability (opens in a new tab)vendor-advisorypatch
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-73940 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-66303)Record last updated .