{"id":"CVE-2021-26858","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-26858","generatedAt":"2026-10-27T22:29:00.463Z","title":"Microsoft Exchange Server Remote Code Execution Vulnerability","description":"Microsoft Exchange Server Remote Code Execution Vulnerability","published":"2021-03-03T00:15:12.000Z","lastModified":"2026-10-01T21:17:17.000Z","status":"Analyzed","sourceIdentifier":"secure@microsoft.com","cvss":{"version":"3.1","score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},"cwe":[],"affected":["microsoft/exchange server"],"epss":{"score":0.93651,"percentile":0.99841,"date":"2026-10-26","history":[]},"kev":{"listed":true,"dateAdded":"2021-11-03","dueDate":"2022-05-03","knownRansomwareCampaignUse":"Known","notes":"Apply updates per vendor instructions.\nReference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-26858"},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"Known to be exploited in the wild (CISA KEV, CISA remediation deadline 3 May 2022). Treat as an emergency change: patch or isolate now, then hunt for prior compromise."},"changes":[],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858","tags":["Patch","Vendor Advisory"],"source":"secure@microsoft.com"},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26858","tags":["US Government Resource"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-26858","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}