# CVE-2026-87696: Microsoft Exchange Server cryptographic signature verification privilege escalation

Source: https://junglewise.ai/threats/cve-2026-87696-improper-verification-of-cryptographic-signature-in-microsoft  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-87696 · Severity: high · CVSS 7.5 · Published 2026-10-13

Microsoft Exchange Server, which handles enterprise email and calendar functions, contains a flaw in how it validates digital signatures. An authorized user on the network can exploit this to gain elevated privileges on the Exchange Server, potentially leading to unauthorized access to email data, calendar information, and system controls.

Technologies: [Microsoft Exchange Server](https://junglewise.ai/threats/technologies/exchange-server), [Microsoft Exchange Server Subscription Edition](https://junglewise.ai/threats/technologies/exchange-server-subscription-edition). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-87696 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87696 being exploited in the wild.

**How severe is CVE-2026-87696?** High severity, with a CVSS score of 7.5, published 13 October 2026.

**Which products and versions are affected?** Microsoft Exchange Server.

**Is there a fix for CVE-2026-87696?** 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-2026-87696 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-87696?** Check whether you run Microsoft Exchange Server or Microsoft Exchange Server Subscription Edition. 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 involves improper verification of cryptographic signatures in Microsoft Exchange Server, allowing privilege escalation over the network. An authenticated network attacker can exploit this flaw to elevate their privileges. The exact vulnerable component and patched versions are not detailed in the available advisory references.

## Affected products

- Microsoft Exchange Server

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-87696](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-87696)

## Related threats

- [Microsoft Exchange Server improper access control spoofing](https://junglewise.ai/threats/cve-2026-118208-improper-access-control-in-microsoft-exchange-server-allows-an)
- [Microsoft Exchange Server improper input validation code execution](https://junglewise.ai/threats/cve-2026-118207-improper-input-validation-in-microsoft-exchange-server-allows-an)
- [Microsoft Exchange Server weak authentication privilege elevation](https://junglewise.ai/threats/cve-2026-118157-weak-authentication-in-microsoft-exchange-server-allows-an)
- [Microsoft Exchange Server privilege elevation via untrusted security decision input](https://junglewise.ai/threats/cve-2026-118154-reliance-on-untrusted-inputs-in-a-security-decision-in-microsoft)
- [Microsoft Exchange Server algorithmic complexity denial of service](https://junglewise.ai/threats/cve-2026-118153-inefficient-algorithmic-complexity-in-microsoft-exchange-server)