CVE-2026-42246: Ruby-Lang Net::imap

High severity, CVSS 7.4. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Ruby-Lang Net::imap: before 0.3.10 (fixed in 0.3.10); from 0.4.0, before 0.4.24 (fixed in 0.4.24); from 0.5.0, before 0.5.14 (fixed in 0.5.14); from 0.6.0, before 0.6.4 (fixed in 0.6.4)

Published 2026-05-09. Last modified 2026-08-24.