{"id":"CVE-2026-41319","revision":"d94fb6d7106f4fe6b3d24abb5ec3f13a","records":[{"revision":"d94fb6d7106f4fe6b3d24abb5ec3f13a","observedAt":"2026-10-25T09:17:35.966+00:00","statement":{"source":"nvd","id":"CVE-2026-41319","aliases":[],"title":"MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext…","description":"MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext-to-TLS trust boundary, enabling SASL authentication mechanism downgrade (e.g., forcing PLAIN instead of SCRAM-SHA-256). The internal read buffer in `SmtpStream`, `ImapStream`, and `Pop3Stream` is not flushed when the underlying stream is replaced with `SslStream` during STARTTLS upgrade, causing pre-TLS attacker-injected data to be processed as trusted post-TLS responses. Version 4.16.0 patches the issue.","state":0,"publishedAt":"2026-04-24T04:16:20.4+00:00","modifiedAt":"2026-06-17T10:46:30.013+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N","score":6.5,"severity":"MEDIUM"},{"system":"CVSS 3.1 · nvd@nist.gov · Primary","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","score":5.9,"severity":"MEDIUM"}],"references":["https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-41319","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-74"],"productCriteria":["cpe:2.3:a:jstedfast:mailkit:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-04-24T04:16:20.400","lastModified":"2026-06-17T10:46:30.013"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-41319","identifiers":["CVE-2026-41319"]},"retained":false,"historicalAffected":[]}],"coverage":[]}