Critical Ruby Vulnerabilities in IMAP and GzipReader Affecting Ubuntu

Two critical vulnerabilities were discovered in Ruby affecting the Net::IMAP client and Zlib::GzipReader. CVE-2026-42258 allows remote attackers to inject arbitrary IMAP commands via CRLF sequences, while CVE-2026-27820 can lead to a buffer overflow through crafted gzip streams. These vulnerabilities impact Ruby 2.3 and could lead to memory corruption or arbitrary code execution. The issues were published on May 9, 2026, and April 16, 2026, respectively. Affected users are advised to update their systems to mitigate these risks. Ubuntu Pro users can receive extended security coverage for these packages. A standard system update will address these vulnerabilities.

Key Points: • CVE-2026-42258 allows remote command injection in the Net::IMAP client. • CVE-2026-27820 can cause buffer overflow and memory corruption in Zlib::GzipReader. • Affected systems include Ruby 2.3 on Ubuntu; updates are available via standard system updates.