# CVE-2026-45584: Microsoft Defender heap buffer overflow

Source: https://junglewise.ai/threats/cve-2026-45584-microsoft-defender-heap-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-20. Updated: 2026-05-20  
License: CC BY 4.0 with a link back

CVE-2026-45584 · Severity: high · CVSS 8.1 · Published 2026-05-20

Microsoft Defender, the built-in security and antivirus software for Windows, contains a critical vulnerability that could allow a remote attacker to take control of a system. By exploiting a memory handling error, an unauthorized user could execute malicious code over the network. This poses a significant risk to data confidentiality and system availability, potentially allowing for full system compromise without any user interaction.

Technologies: [Microsoft Defender](https://junglewise.ai/threats/technologies/defender). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-45584 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-45584 being exploited in the wild.

**How severe is CVE-2026-45584?** High severity, with a CVSS score of 8.1, published 20 May 2026.

**Which products and versions are affected?** Microsoft Defender.

**Is there a fix for CVE-2026-45584?** 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-2026-45584 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-45584?** Check whether you run Microsoft Defender. 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 Defender. The vulnerability is reachable over the network and does not require user interaction or administrative privileges (PR:N/UI:N). However, the attack complexity is rated as high (AC:H), suggesting specific timing or environmental conditions are required for successful exploitation. If successfully exploited, an attacker can achieve remote code execution (RCE) with the privileges of the Defender service, leading to a total loss of confidentiality, integrity, and availability. Microsoft has released information regarding this vulnerability via their Security Update Guide.

## Affected products

- Microsoft Defender

## Timeline

- 2026-05-20: disclosed
- 2026-05-20: advisory

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45584](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45584)

## Related threats

- [Microsoft Defender null pointer dereference remote code execution](https://junglewise.ai/threats/cve-2026-122194-null-pointer-dereference-in-microsoft-defender-allows-an)
- [Microsoft Defender out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-105726-out-of-bounds-read-in-microsoft-defender-allows-an-authorized)
- [Microsoft Defender Malware Protection Engine elevation of privilege](https://junglewise.ai/threats/cve-2026-69414-microsoft-defender-malware-protection-engine-elevation-of)
- [Microsoft Defender denial of service](https://junglewise.ai/threats/cve-2026-45498-microsoft-defender-denial-of-service)
- [Microsoft Defender privilege escalation via improper link resolution](https://junglewise.ai/threats/cve-2026-41091-microsoft-defender-privilege-escalation-via-improper-link)