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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)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
CWE
  • CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Assigner
References
Impacted products
Vendor Product Version
jstedfast MailKit Affected: < 4.16.0
Create a notification for this product.
Show details on NVD website
To clipboard 

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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)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
CWE
  • CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Assigner
References
Impacted products
Vendor Product Version
jstedfast MailKit Affected: < 4.16.0
Create a notification for this product.
Show details on NVD website
To clipboard 

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