# CVE-2026-85818: Windows Schannel cryptographic signature verification bypass

Source: https://junglewise.ai/threats/cve-2026-85818-improper-verification-of-cryptographic-signature-in-windows  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-85818 · Severity: critical · CVSS 9 · Published 2026-10-13

Windows Schannel, the SSL/TLS cryptographic component used to secure network communications, fails to properly verify cryptographic signatures. An attacker can exploit this flaw over the network to spoof legitimate services and intercept encrypted traffic, potentially leading to credential theft or unauthorized access to sensitive systems and data.

Technologies: [Microsoft Windows 11 23h2](https://junglewise.ai/threats/technologies/windows-11-23h2), [Microsoft Windows 11 24h2](https://junglewise.ai/threats/technologies/windows-11-24h2), [Microsoft Windows 11 25h2](https://junglewise.ai/threats/technologies/windows-11-25h2), [Microsoft Windows 11 26h1](https://junglewise.ai/threats/technologies/windows-11-26h1), [Microsoft Windows 11 26h2](https://junglewise.ai/threats/technologies/windows-11-26h2), [Microsoft Windows Server 2022](https://junglewise.ai/threats/technologies/windows-server-2022), [Microsoft Windows Server 2025](https://junglewise.ai/threats/technologies/windows-server-2025). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-85818 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85818 being exploited in the wild.

**How severe is CVE-2026-85818?** Critical severity, with a CVSS score of 9, published 13 October 2026.

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

**Is there a fix for CVE-2026-85818?** 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-2026-85818 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-85818?** Check whether you run Microsoft Windows 11 23h2, Microsoft Windows 11 24h2, Microsoft Windows 11 25h2 or one of the others listed. 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

Windows Schannel contains an improper cryptographic signature verification flaw in its TLS/SSL implementation. An unauthenticated attacker can perform a spoofing attack over the network by presenting forged certificates or manipulated cryptographic signatures that are not properly validated. This breaks the integrity guarantee of the TLS protocol, allowing man-in-the-middle attacks and credential harvesting.

## Affected products

- Windows Schannel

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85818](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85818)

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