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CVE-2026-42257

9.8 · CRITICAL

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby.

Published May 9, 2026CWE-77EPSS 0.52%

Overview

CVE-2026-42257 is a critical-severity vulnerability. It was published on May 9, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.4.24, 0.5.14, and 0.6.4, several Net::IMAP commands accept a raw string argument that is sent to the server without validation or escaping. If this string is derived from user-controlled input, it may contain contain CRLF sequences, which an attacker can use to inject arbitrary IMAP commands. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/ruby/net-imap/releases/tag/v0.4.24GitHubgithub.com/ruby/net-imap/releases/tag/v0.5.14GitHubgithub.com/ruby/net-imap/releases/tag/v0.6.4GitHubgithub.com/ruby/net-imap/security/advisories/GHSA-hm49-wcqc-g2xg

How CyberStrike helps

Frequently asked questions

What is CVE-2026-42257?

CVE-2026-42257 is a critical-severity vulnerability. It was published on May 9, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-42257?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-42257?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-42257?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-42257 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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