# CVE-2026-72940: Microsoft Windows Schannel heap buffer overflow

Source: https://junglewise.ai/threats/cve-2026-72940-microsoft-windows-schannel-heap-buffer-overflow  
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-2026-72940 · Severity: high · CVSS 8.8 · Published 2026-09-08

Windows Schannel is the cryptographic security component used to protect network communications in Windows systems. A heap buffer overflow vulnerability allows an attacker to execute arbitrary code remotely on affected systems with elevated privileges, potentially compromising confidential data and system operations.

Technologies: [Microsoft Windows (Schannel)](https://junglewise.ai/threats/technologies/windows-schannel). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-72940 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-72940 being exploited in the wild.

**How severe is CVE-2026-72940?** High severity, with a CVSS score of 8.8, published 8 September 2026.

**Which products and versions are affected?** Microsoft Windows Schannel.

**Is there a fix for CVE-2026-72940?** 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-2026-72940 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-72940?** Check whether you run Microsoft Windows (Schannel). 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

A heap-based buffer overflow exists in Windows Schannel, Microsoft's TLS/SSL implementation component. The vulnerability can be triggered over the network without authentication, allowing an attacker to corrupt heap memory and achieve arbitrary code execution. The attack vector is network-based with no authentication or user interaction required. A successful exploit grants the attacker code execution in the security context of the affected process, posing a critical risk to system and data integrity. Patches are available from Microsoft.

## Affected products

- Microsoft Windows Schannel

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72940](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72940)

## Related threats

- [Microsoft Windows Schannel null pointer dereference](https://junglewise.ai/threats/cve-2026-70575-microsoft-windows-schannel-null-pointer-dereference)