# CVE-2026-55005: Microsoft Exchange Server heap overflow remote code execution

Source: https://junglewise.ai/threats/cve-2026-55005-microsoft-exchange-server-heap-overflow-remote-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-55005 · Severity: high · CVSS 8.8 · Published 2026-07-14

A security vulnerability has been identified in Microsoft Exchange Server, the platform used by organizations for email and calendaring. An attacker with basic user credentials could exploit this flaw to take control of the server and execute malicious commands. This could lead to a total compromise of the email system, including unauthorized access to sensitive communications and disruption of business operations.

Technologies: [Microsoft Exchange Server 2016](https://junglewise.ai/threats/technologies/exchange-server-2016), [Microsoft Exchange Server 2019](https://junglewise.ai/threats/technologies/exchange-server-2019), [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-2026-55005 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55005 being exploited in the wild.

**How severe is CVE-2026-55005?** High severity, with a CVSS score of 8.8, published 14 July 2026.

**Which products and versions are affected?** Microsoft Exchange Server 2016 15.01.0.0 to 15.01.2507.071; Microsoft Exchange Server 2019 15.02.0.0 to 15.02.1544.043; Microsoft Exchange Server Subscription Edition 15.02.0.0 to 15.02.2562.045.

**Is there a fix for CVE-2026-55005?** 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-2026-55005 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-55005?** Check whether you run Microsoft Exchange Server 2016, Microsoft Exchange Server 2019 or Microsoft Exchange Server Subscription Edition at an affected version. 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 (CWE-122) exists in Microsoft Exchange Server. The vulnerability is reachable over the network and requires low-privileged user authentication (PR:L), but no user interaction. By sending a specially crafted request to the server, an attacker can trigger the overflow to achieve remote code execution (RCE) in the context of the Exchange service. Affected versions include Exchange Server 2016, 2019, and the Subscription Edition; Microsoft has released security updates to address this issue.

## Affected products

- Microsoft Exchange Server 2016 Cumulative Update 23 15.01.0.0 to 15.01.2507.071
- Microsoft Exchange Server 2019 Cumulative Update 14 15.02.0.0 to 15.02.1544.043
- Microsoft Exchange Server 2019 Cumulative Update 15 15.02.0.0 to 15.02.1748.048
- Microsoft Exchange Server Subscription Edition RTM 15.02.0.0 to 15.02.2562.045

## Timeline

- 2026-07-14: disclosed
- 2026-07-14: advisory: Microsoft released security updates for affected versions.

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55005](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55005)

## Related threats

- [Microsoft Exchange Server cryptographic signature verification privilege escalation](https://junglewise.ai/threats/cve-2026-87696-improper-verification-of-cryptographic-signature-in-microsoft)
- [Microsoft Exchange Server privilege escalation via untrusted control sphere](https://junglewise.ai/threats/cve-2026-87695-inclusion-of-functionality-from-untrusted-control-sphere-in)
- [Microsoft Exchange Server deserialization privilege elevation](https://junglewise.ai/threats/cve-2026-87692-deserialization-of-untrusted-data-in-microsoft-exchange-server)
- [Microsoft Exchange Server privilege escalation via NTLM relay to MRSProxy](https://junglewise.ai/threats/cve-2026-62911-microsoft-exchange-server-privilege-escalation-via-ntlm-relay-to)
- [Microsoft Exchange Server deserialization privilege escalation](https://junglewise.ai/threats/cve-2026-55009-microsoft-exchange-server-deserialization-privilege-escalation)