{"id":"CVE-2021-1730","aliases":["EUVD-2021-7194","GHSA-mp5r-32pv-q987"],"status":"published","title":"Microsoft Exchange Server Spoofing Vulnerability","description":"\u003cp\u003eA spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.\u003c/p\u003e\n\u003cp\u003eThis update addresses this vulnerability.\u003c/p\u003e\n\u003cp\u003eTo prevent these types of attacks, Microsoft recommends customers to download inline images from different DNSdomains than the rest of OWA. Please see further instructions in the FAQ to put in place this mitigations.\u003c/p\u003e","severity":{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.01817,"percentile":0.79017,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"published":"2021-02-25T23:01:30Z","modified":"2026-06-17T03:32:27Z","products":[{"vendor":"microsoft","product":"exchange_server"},{"vendor":"microsoft","product":"microsoft exchange server 2016 cumulative update 18"},{"vendor":"microsoft","product":"microsoft exchange server 2019 cumulative update 7"}],"references":[{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1730","tags":["x_refsource_MISC","x_transferred","Patch","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-1730"},{"url":"https://github.com/advisories/GHSA-mp5r-32pv-q987"}],"sources":{"cve":[{"id":"CVE-2021-1730","title":"Microsoft Exchange Server Spoofing Vulnerability","description":"\u003cp\u003eA spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.\u003c/p\u003e\n\u003cp\u003eThis update addresses this vulnerability.\u003c/p\u003e\n\u003cp\u003eTo prevent these types of attacks, Microsoft recommends customers to download inline images from different DNSdomains than the rest of OWA. Please see further instructions in the FAQ to put in place this mitigations.\u003c/p\u003e","status":"published","published":"2021-02-25T23:01:30Z","modified":"2024-08-03T16:18:11.528Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C","level":"medium","assessor":"cna"}],"updated_at":"2026-11-02T14:33:08.811269Z"}],"euvd":[{"id":"EUVD-2021-7194","description":"\u003cp\u003eA spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.\u003c/p\u003e\n\u003cp\u003eThis update addresses this vulnerability.\u003c/p\u003e\n\u003cp\u003eTo prevent these types of attacks, Microsoft recommends customers to download inline images from different DNSdomains than the rest of OWA. Please see further instructions in the FAQ to put in place this mitigations.\u003c/p\u003e","status":"published","published":"2021-02-25T23:01:30Z","modified":"2024-08-03T16:18:11Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C","level":"medium"}],"updated_at":"2026-11-03T03:25:15.150715Z"}],"ghsa":[{"id":"GHSA-mp5r-32pv-q987","title":"Microsoft Exchange Server Spoofing Vulnerability This CVE ID is unique from CVE-2021-24085.","description":"Microsoft Exchange Server Spoofing Vulnerability This CVE ID is unique from CVE-2021-24085.","status":"published","published":"2022-05-24T17:43:10Z","modified":"2024-01-07T05:05:09Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T14:55:20.878476Z"}],"nvd":[{"id":"CVE-2021-1730","description":"\u003cp\u003eA spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.\u003c/p\u003e\n\u003cp\u003eThis update addresses this vulnerability.\u003c/p\u003e\n\u003cp\u003eTo prevent these types of attacks, Microsoft recommends customers to download inline images from different DNSdomains than the rest of OWA. Please see further instructions in the FAQ to put in place this mitigations.\u003c/p\u003e","status":"published","published":"2021-02-25T23:15:13.79Z","modified":"2026-06-17T03:32:27.357Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"2.0","score":5.8,"vector":"AV:N/AC:M/Au:N/C:P/I:P/A:N","level":"medium","assessor":"primary"}],"updated_at":"2026-11-02T14:06:50.399901Z"}]}}