{"schemaVersion":3,"id":"CVE-2021-38371","aliases":["UBUNTU-CVE-2021-38371","USN-6881-1","DEBIAN-CVE-2021-38371"],"status":"published","duplicateOf":null,"title":null,"description":"The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.","dates":{"published":"2021-08-10T14:06:09.000Z","modified":"2025-11-03T21:45:12.326Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":7.5,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","exploitability":10,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","exploitability":10,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","exploitability":null,"impact":null,"computed":false},{"version":"2.0","versionLabel":"v2.0","source":"NVD","score":5,"severity":"medium","vector":"AV:N/AC:L/Au:N/C:N/I:P/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.01996,"percentile":0.80414,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.01996},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.01996,"percentile":0.80414}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.01996,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.01996,"percentile":0.80414}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-74","name":"Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')","description":"The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.","type":"weakness","status":"Incomplete","abstraction":"Class","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/74.html"}],"affected":[{"vendor":"debian","product":"exim4","name":"exim4","label":"exim4","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/exim4","purlType":"deb","versions":[{"text":"< 4.95~RC2-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.95~RC2-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"exim4","name":"exim4","label":"exim4","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/exim4","purlType":"deb","versions":[{"text":"< 4.82-3ubuntu2.4+esm8","noFixRecorded":false,"fixedIn":null},{"text":"< 4.86.2-2ubuntu2.6+esm7","noFixRecorded":false,"fixedIn":null},{"text":"< 4.90.1-1ubuntu1.10+esm4","noFixRecorded":false,"fixedIn":null},{"text":"< 4.93-13ubuntu1.11","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.82-3ubuntu2.4+esm8 | < 4.86.2-2ubuntu2.6+esm7 | < 4.90.1-1ubuntu1.10+esm4 | < 4.93-13ubuntu1.11","eol":null,"hubHref":null},{"vendor":"exim","product":"exim","name":"Exim","label":"exim","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≤ 4.94.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"≤ 4.94.2","eol":{"isEol":null,"eolDate":null,"matchMethod":"cpe","cycle":null,"product":{"name":"exim","label":"Exim","category":"server-app"}},"hubHref":"/vendor/exim/exim"}],"affectedCount":3,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://nostarttls.secvuln.info","label":"nostarttls.secvuln.info","hostname":"nostarttls.secvuln.info","tags":["X Refsource MISC","REPORT","Tool Signature"]},{"url":"https://www.exim.org","label":"www.exim.org","hostname":"www.exim.org","tags":["X Refsource MISC","Product"]},{"url":"https://www.exim.org/static/doc/security/CVE-2021-38371.txt","label":"www.exim.org/static/doc/security/CVE-2021-38371.txt","hostname":"www.exim.org","tags":["X Refsource MISC","REPORT","Broken Link","Vendor Advisory"]},{"url":"https://lists.debian.org/debian-lts-announce/2024/10/msg00029.html","label":"lists.debian.org/debian-lts-announce/2024/10/msg00029.html","hostname":"lists.debian.org","tags":[]},{"url":"https://ubuntu.com/security/CVE-2021-38371","label":"ubuntu.com/security/CVE-2021-38371","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-38371","label":"www.cve.org/CVERecord?id=CVE-2021-38371","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://ubuntu.com/security/notices/USN-6881-1","label":"ubuntu.com/security/notices/USN-6881-1","hostname":"ubuntu.com","tags":["Advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-38371","label":"security-tracker.debian.org/tracker/CVE-2021-38371","hostname":"security-tracker.debian.org","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":["DLA-3938-1"],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2021-08-10T14:06:09.000Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2025-11-03T21:45:12.326Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":30,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T06:25:16.600Z","stale":false,"partial":false}}