Ruby IMAP Library Vulnerabilities Expose Users to MITM Attacks

Ruby IMAP Library Vulnerabilities Expose Users to MITM Attacks

First seen 16 Jun 2026, 11:21 UTC •UbuntuLinuxsecurity •89% similarity •72.5

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Two critical vulnerabilities were discovered in Ruby's Net::IMAP library affecting Ubuntu 18.04 and 16.04 LTS. CVE-2026-42246 allows remote attackers to perform machine-in-the-middle attacks by bypassing TLS encryption. CVE-2026-42257 enables attackers to inject arbitrary IMAP commands due to improper validation of string arguments. These vulnerabilities could lead to unauthorized access to network services. Affected users are urged to update their systems to mitigate risks. The vulnerabilities were published on May 9, 2026, and are currently being addressed through standard system updates. Ubuntu Pro users have access to long-term security coverage for affected packages.

Key Points: • Two vulnerabilities in Ruby's Net::IMAP library could lead to serious security breaches. • CVE-2026-42246 allows for machine-in-the-middle attacks, while CVE-2026-42257 enables command injection. • Affected systems include Ubuntu 18.04 and 16.04 LTS; users should update immediately.

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Timeline

2026-05-09
CVE-2026-42246 and CVE-2026-42257 published
Two vulnerabilities in Ruby's Net::IMAP library were disclosed, affecting TLS encryption and command validation.
Ubuntu
2026-06-15
Security advisory issued by Ubuntu
Ubuntu published USN-8431-1 detailing the vulnerabilities and urging users to update their systems.
Ubuntu
2026-06-16
Linuxsecurity reports on Ruby vulnerabilities
Linuxsecurity provided an advisory on the same vulnerabilities, emphasizing the need for updates on affected Ubuntu versions.
Linuxsecurity

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