How severe is CVE-2021-34522?

CVE-2021-34522 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-34522 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34522?

CVE-2021-34522 affects Microsoft Malware Protection Engine. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-34522?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-34522 published?

CVE-2021-34522 was published on 2021-07-14 and last updated on 2026-06-17.

CVE-2021-34522

CVE-2021-34522 is a high-severity vulnerability in Microsoft Malware Protection Engine with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 9.3
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Malware Protection Engine
Published: 2021-07-14
Last modified: 2026-06-17

Description

Microsoft Defender Remote Code Execution Vulnerability

Frequently asked questions

What is CVE-2021-34522?: Microsoft Defender Remote Code Execution Vulnerability
How severe is CVE-2021-34522?: CVE-2021-34522 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-34522 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34522?: CVE-2021-34522 affects Microsoft Malware Protection Engine. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-34522?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-34522 published?: CVE-2021-34522 was published on 2021-07-14 and last updated on 2026-06-17.

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34522

Affected products (1)

cpe:2.3:a:microsoft:malware_protection_engine:*:*:*:*:*:*:*:*

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