Quick answers
- Is CVE-2026-66307 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-66307 being exploited in the wild.
- How severe is CVE-2026-66307?
- High severity, with a CVSS score of 7.5, published 8 September 2026.
- Which products and versions are affected?
- Microsoft Skype for Business.
- Is there a fix for CVE-2026-66307?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-66307 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-66307?
- Check whether you run Microsoft Skype for Business. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An integer underflow (wrap or wraparound) vulnerability exists in Skype for Business that allows an unauthenticated attacker to send specially crafted network packets to trigger a denial of service condition. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction. Successful exploitation causes service disruption, preventing users from accessing Skype for Business functionality. The attack vector is network-based, making it a significant concern for internet-facing deployments or those within corporate networks.
Affected products
- Microsoft Skype for Business
Timeline
- 2026-09-08: disclosed