CVE-2021-28481

CRITICALNVD 9.89.8—Elevated

9.8

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 97.1%
KEV: Not listed

Published

April 13, 2021

Last Modified

November 21, 2024

References (2)

secure@microsofthttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28481
af854a3a-2127-422b-91ae-364da2661108https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28481

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Microsoft MSRCCVE-2021-284812021-04-13
Microsoft Exchange Server Remote Code Execution Vulnerability

Data Freshness Timeline

(refreshed 11× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-07 15:23 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-29 13:42 UTCEPSS rescore
2026-05-28 13:43 UTCEPSS rescore
2026-05-28 13:43 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

Nucleihttp/cves/2021/CVE-2021-28481.yaml
First seen Jan 1, 2021
Microsoft Exchange - Pre-Auth SSRF / ACL Bypass (ProxyNotFound)
Open source ↗

Frequently asked(5)

What is CVE-2021-28481?

CVE-2021-28481 is a critical vulnerability published on April 13, 2021. Microsoft Exchange Server Remote Code Execution Vulnerability

When was CVE-2021-28481 disclosed?

CVE-2021-28481 was first published in the National Vulnerability Database on April 13, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-28481 actively exploited?

CVE-2021-28481 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 97.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-28481?

CVE-2021-28481 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-28481?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-28481, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-28481

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