{"id":"CVE-2026-30227","aliases":["GHSA-g7hc-96xr-gvvx"],"url":"https://o3.security/vulnerability/CVE-2026-30227","summary":"MimeKit: CRLF Injection in Quoted Local-Part Enables SMTP Command Injection and Email Forgery","details":"MimeKit is a C# library which may be used for the creation and parsing of messages using the Multipurpose Internet Mail Extension (MIME), as defined by numerous IETF specifications. Prior to version 4.15.1, a CRLF injection vulnerability in MimeKit allows an attacker to embed \\r\\n into the SMTP envelope address local-part (when the local-part is a quoted-string). This is non-compliant with RFC 5321 and can result in SMTP command injection (e.g., injecting additional RCPT TO / DATA / RSET commands) and/or mail header injection, depending on how the application uses MailKit/MimeKit to construct and send messages. The issue becomes exploitable when the attacker can influence a MailboxAddress (MAIL FROM / RCPT TO) value that is later serialized to an SMTP session. RFC 5321 explicitly defines the SMTP mailbox local-part grammar and does not permit CR (13) or LF (10) inside Quoted-string (qtextSMTP and quoted-pairSMTP ranges exclude control characters). SMTP commands are terminated by <CRLF>, making CRLF injection in command arguments particularly dangerous. This issue has been patched in version 4.15.1.","published":"2026-03-06T21:07:49.691Z","modified":"2026-07-15T01:49:12.046005609Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"NuGet","name":"MimeKit","fixedVersion":"4.15.1"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/30xxx/CVE-2026-30227.json"},{"type":"ADVISORY","url":"https://github.com/jstedfast/MimeKit/security/advisories/GHSA-g7hc-96xr-gvvx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-30227"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-15T01:49:12.046005609Z"}}