# CVE-2026-118157: Microsoft Exchange Server weak authentication privilege elevation

Source: https://junglewise.ai/threats/cve-2026-118157-weak-authentication-in-microsoft-exchange-server-allows-an  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-118157 · Severity: high · CVSS 7.2 · Published 2026-11-10

Microsoft Exchange Server, which handles corporate email and calendar services, contains a weak authentication mechanism that allows authorized users to escalate their privileges on the network. An attacker with legitimate credentials could exploit this to gain elevated access and potentially access sensitive business communications or perform unauthorized administrative actions.

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

## Quick answers

**Is CVE-2026-118157 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118157 being exploited in the wild.

**How severe is CVE-2026-118157?** High severity, with a CVSS score of 7.2, published 10 November 2026.

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

**Is there a fix for CVE-2026-118157?** 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-2026-118157 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-118157?** Check whether you run Microsoft Exchange Server. 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 weak authentication in Microsoft Exchange Server that permits privilege escalation over a network. An attacker with valid credentials can exploit this flaw to obtain elevated privileges, likely gaining unauthorized access to administrative functions or sensitive mailbox data. The attack requires network access and prior authentication.

## Affected products

- Microsoft Exchange Server

## Timeline

- 2026-11-10: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-118157](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-118157)

## 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 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)
- [Microsoft Exchange Server CSRF spoofing](https://junglewise.ai/threats/cve-2026-118152-cross-site-request-forgery-csrf-in-microsoft-exchange-server)