========================================================================== Ubuntu Security Notice USN-8431-1 June 15, 2026
ruby2.3, ruby2.5 vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
Summary:
Ruby could allow unintended access to network services.
Software Description:
- ruby2.5: Object-oriented scripting language
- ruby2.3: 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 18.04 LTS
libruby2.5 2.5.1-1ubuntu1.16+esm8
Available with Ubuntu Pro
ruby2.5 2.5.1-1ubuntu1.16+esm8
Available with Ubuntu Pro
Ubuntu 16.04 LTS
libruby2.3 2.3.1-2~ubuntu16.04.16+esm14
Available with Ubuntu Pro
ruby2.3 2.3.1-2~ubuntu16.04.16+esm14
Available with Ubuntu Pro
In general, a standard system update will make all the necessary changes.
References:
https://ubuntu.com/security/notices/USN-8431-1
CVE-2026-42246, CVE-2026-42257
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