CVE-2026-80213

A flaw was found in the resolv gem. This vulnerability arises from the incorrect handling of DNS label lengths during message encoding. A remote attacker could exploit this by providing a specially crafted hostname to an application utilizing the resolv gem. This could lead to the bypass of security controls such as allowlists and egress checks, as well as DNS cache poisoning, where a recursive resolver caches an attacker-chosen name instead of the intended one. This also results in inaccurate DNS logs.

This is a Moderate impact vulnerability in the Ruby resolv gem, which is part of the Ruby standard library. This flaw allows for DNS allowlist and egress bypass, and cache poisoning. When an application processes attacker-controlled hostnames, it can result in DNS queries for unintended domains, potentially circumventing network access restrictions or domain validation checks.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.