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Ubuntu 16.04 Ruby Critical IMAP Injection Buffer Overflow USN-8556-1

ubuntu
Calendar Grey July 16, 2026
Scroller Ubuntu Esm H88
Security issues in Ruby for Ubuntu 16.04 LTS addressed with recommended updates to prevent exploitation.
Several security issues were fixed in Ruby.

Summary

Several security issues were fixed in Ruby.

Software Description:

- ruby2.3: Object-oriented scripting language

Details:

It was discovered that the Net::IMAP client in Ruby did not properly

sanitize Symbol arguments passed to IMAP commands. A remote attacker

controlling a malicious IMAP server, or able to influence command

arguments, could use this to inject arbitrary IMAP commands via CRLF

sequences. (CVE-2026-42258)

It was discovered that the Zlib::GzipReader in Ruby did not correctly

ensure sufficient buffer capacity in the zstream_buffer_ungets function.

An attacker could use this to craft a gzip stream that, when processed,

could cause a buffer overflow, resulting in memory corruption and possibly

arbitrary code execution. (CVE-2026-27820)

Topics%20covered

Topics Covered

security advisory buffer overflow critical Ubuntu remote command injection ruby2.3

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 16.04 LTS
  libruby2.3                      2.3.1-2~ubuntu16.04.16+esm15
                                  Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References

https://ubuntu.com/security/notices/USN-8556-1

CVE-2026-27820, CVE-2026-42258

Severity
critical
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8556-1

Topics%20covered

Topics Covered

security advisory buffer overflow critical Ubuntu remote command injection ruby2.3

Package Information

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