# CVE-2026-69646: Microsoft Skype for Business cryptographic signature spoofing

Source: https://junglewise.ai/threats/cve-2026-69646-microsoft-skype-for-business-cryptographic-signature-spoofing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-69646 · Severity: high · CVSS 8.3 · Published 2026-09-08

Skype for Business, a unified communications platform used by enterprises for instant messaging and video conferencing, contains a flaw in cryptographic signature verification. An attacker on an adjacent network could forge communication signatures and impersonate legitimate users or services, potentially leading to unauthorized access, credential theft, or disruption of business communications.

Technologies: [Microsoft Skype for Business](https://junglewise.ai/threats/technologies/skype-for-business). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-69646 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-69646 being exploited in the wild.

**How severe is CVE-2026-69646?** High severity, with a CVSS score of 8.3, published 8 September 2026.

**Which products and versions are affected?** Microsoft Skype for Business.

**Is there a fix for CVE-2026-69646?** 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-2026-69646 attacked?** It is attacked from the adjacent network.

**Am I affected by CVE-2026-69646?** 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

The vulnerability is an improper cryptographic signature verification issue in Skype for Business that allows signature spoofing attacks. An attacker positioned on an adjacent network (not requiring internet routing) can forge valid-appearing signatures to impersonate other users or services. The attack requires network adjacency but does not appear to require prior authentication or user interaction. Successful exploitation could allow an attacker to spoof communications, potentially leading to social engineering, credential harvesting, or unauthorized access to sensitive conversations. A patch from Microsoft is expected to be available.

## Affected products

- Microsoft Skype for Business

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69646](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69646)

## Related threats

- [Microsoft Skype for Business and Lync privilege escalation](https://junglewise.ai/threats/cve-2026-85873-improper-authorization-in-skype-for-business-and-microsoft-lync)
- [Microsoft Skype for Business cross-site scripting in web page generation](https://junglewise.ai/threats/cve-2026-69642-microsoft-skype-for-business-cross-site-scripting-in-web-page)
- [Microsoft Skype for Business out-of-bounds read](https://junglewise.ai/threats/cve-2026-66308-microsoft-skype-for-business-out-of-bounds-read)
- [Microsoft Skype for Business integer underflow denial of service](https://junglewise.ai/threats/cve-2026-66307-microsoft-skype-for-business-integer-underflow-denial-of-service)
- [Microsoft Skype for Business information disclosure in error messages](https://junglewise.ai/threats/cve-2026-66306-microsoft-skype-for-business-information-disclosure-in-error)