CVE-2026-42246

High

Description

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.

SeverityHigh

CVSS7.4

Exploit probability—

ProductRuby-lang Net\

PublishedMay 9, 2026

First seenMay 9, 2026

Weakness typeCWE-392CWE-392 CWE-393CWE-393 CWE-754CWE-754 CWE-636CWE-636 CWE-841CWE-841

How to fix

Update

ruby-lang net\0.3.10, 0.4.24, 0.5.14, 0.6.4 or later

Vendor advisories

Affected products

Product	Affected versions	Fixed in
ruby-lang net\	\ ≤ v < 0.3.10, 0.4.0 ≤ v < 0.4.24, 0.5.0 ≤ v < 0.5.14, 0.6.0 ≤ v < 0.6.4	0.3.10, 0.4.24, 0.5.14, 0.6.4

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