CVE-2021-26857

HIGHNVD 7.89.0▲

7.8

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS v3: 7.8
EG Score: 9.0(high)
EPSS: 97.4%
KEV: ⚠ Exploited

Published

March 3, 2021

Last Modified

December 18, 2025

References (3)

secure@microsofthttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857
af854a3a-2127-422b-91ae-364da2661108https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857
134c704f-9b21-4f2e-91b3-4a467353bcc0https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

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-2021-268572021-03-02
Microsoft Exchange Server Remote Code Execution Vulnerability

Data Freshness Timeline

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

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-27 20:35 UTCkev_newly_listed
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 19:14 UTCEG score recompute
2026-05-26 19:14 UTCVendor advisory
2026-05-26 19:14 UTCGHSA enrichment
2026-05-26 19:13 UTCkev_newly_listed
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-25 04:07 UTCOSV refresh

Frequently asked(6)

What is CVE-2021-26857?

CVE-2021-26857 is a high vulnerability published on March 3, 2021. Microsoft Exchange Server Remote Code Execution Vulnerability

When was CVE-2021-26857 disclosed?

CVE-2021-26857 was first published in the National Vulnerability Database on March 3, 2021, with the most recent update on December 18, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-26857 actively exploited?

Yes. CISA added CVE-2021-26857 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Microsoft Exchange Server. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.

What is the CVSS score of CVE-2021-26857?

CVE-2021-26857 has a CVSS v3 base score of 7.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.

Which products are affected by CVE-2021-26857?

CVE-2021-26857 affects Microsoft Exchange Server. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.

How do I remediate CVE-2021-26857?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-26857, 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-2021-26857

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