ESB-2026.6635

=========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2026.6635 USN-8431-1: Ruby vulnerabilities 16 June 2026 =========================================================================== AUSCERT Security Bulletin Summary --------------------------------- Product: Ruby Publisher: Ubuntu Operating System: Ubuntu Resolution: Patch/Upgrade CVE Names: CVE-2026-42246 CVE-2026-42257 Original Bulletin: https://ubuntu.com/security/notices/USN-8431-1 Comment: CVSS (Max): 9.8 CVE-2026-42257 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) CVSS Source: NIST Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H EPSS (Max): 0.4% (33rd) CVE-2026-42246 2026-06-15 - --------------------------BEGIN INCLUDED TEXT-------------------- USN-8431-1: Ruby vulnerabilities Publication date 15 June 2026 Overview Ruby could allow unintended access to network services. Releases 18.04 LTS 16.04 LTS --------------------------------------------------------------------------------- Open side navigation Packages o ruby2.3 - Object-oriented scripting language o ruby2.5 - Object-oriented scripting language Details It was discovered that Ruby's Net::IMAP library did not properly verify that Transport Layer Security (TLS) encryption was started after issuing a STARTTLS command. A remote attacker could possibly use this issue to perform a machine-in-the-middle attack and silently bypass TLS encryption. ( CVE-2026-42246 ) It was also discovered that Ruby's Net::IMAP library did not validate string arguments passed to certain commands. A remote attacker could possibly use this issue to inject arbitrary IMAP commands. ( CVE-2026-42257 ) Update instructions The problem can be corrected by updating your system to the following package versions: Ubuntu Package Version Release libruby2.5 - 2.5.1-1ubuntu1.16+esm8 Ubuntu Pro Fix available with 18.04 LTS Ubuntu Pro . bionic ruby2.5 - 2.5.1-1ubuntu1.16+esm8 Ubuntu Pro Fix available with Ubuntu Pro . libruby2.3 - 2.3.1-2~ubuntu16.04.16+esm14 Ubuntu Pro Fix available 16.04 LTS with Ubuntu Pro via Legacy Support add-on. xenial ruby2.3 - 2.3.1-2~ubuntu16.04.16+esm14 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. --------------------------------------------------------------------------------- References o CVE-2026-42257 o CVE-2026-42246 - --------------------------END INCLUDED TEXT---------------------- You have received this e-mail bulletin as a result of your organisation's registration with AUSCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AUSCERT's members. As AUSCERT did not write the document quoted above, AUSCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AUSCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://portal.auscert.org.au/bulletins/ =========================================================================== AUSCERT The University of Queensland, Brisbane QLD 4072 Australia e: auscert@auscert.org.au t: +61 (0)7 3365 4417 Allies in Cyber Security ===========================================================================