Ruby vulnerabilities

Summary

It was discovered that Ruby's Net::IMAP library did not properly verify that TLS encryption was started after issuing a STARTTLS command. A remote attacker could use this to perform a machine-in-the-middle attack and silently bypass TLS encryption. (CVE-2026-42246) It was discovered that Ruby's Net::IMAP library did not validate string arguments passed to certain commands. A remote attacker could use this to inject arbitrary IMAP commands. (CVE-2026-42257) It was discovered that Ruby's Net::IMAP library was vulnerable to a denial of service attack when authenticating with SCRAM-SHA1 or SCRAM-SHA256. A hostile server could send a very large iteration count value to cause excessive computation in the client. This issue only affected ruby3.3. (CVE-2026-42256) Affected Ubuntu releases: 26.04, 24.04, 22.04, 20.04. CVEs: CVE-2026-42256, CVE-2026-42246, CVE-2026-42257.