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2 vulnerabilities found for mailkit by jstedfast
CVE-2026-41319 (GCVE-0-2026-41319)
Vulnerability from nvd – Published: 2026-04-24 03:07 – Updated: 2026-04-25 01:46
VLAI
Title
MailKit has STARTTLS Response Injection via unflushed stream buffer that enables SASL mechanism downgrade
Summary
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.
Severity
6.5 (Medium)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/jstedfast/MailKit/security/adv… | x_refsource_CONFIRM |
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CVE-2026-41319 (GCVE-0-2026-41319)
Vulnerability from cvelistv5 – Published: 2026-04-24 03:07 – Updated: 2026-04-25 01:46
VLAI
Title
MailKit has STARTTLS Response Injection via unflushed stream buffer that enables SASL mechanism downgrade
Summary
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.
Severity
6.5 (Medium)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/jstedfast/MailKit/security/adv… | x_refsource_CONFIRM |
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