CVE-2026-42246 HIGH

CVE-2026-42246: net-imap vulnerable to STARTTLS stripping via invalid response timing

Vendor Ruby
Product net-imap
Weakness CWE-392
Published May 9, 2026
Last update June 30, 2026

CVSS base score

7.6/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return "successfully", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4.

Key dates

02Disclosure timeline

May 9, 2026 CVE published
June 30, 2026 Record updated