{"id":"CVE-2026-80212","title":"An issue was discovered in the resolv gem before 0.7.2 for Ruby","summary":"An issue was discovered in the resolv gem before 0.7.2 for Ruby. Resolv::DNS::Resource.get_class, Resolv::DNS::Resource::Generic.create, and Resolv::DNS::SvcParam::Generic.create generate a new class for each unknown DNS resource record …","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-770"],"published":"2026-08-27","updated":"2026-09-09","sourceUpdated":"2026-09-09T16:04:24.933","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-80212","references":[{"url":"https://github.com/ruby/resolv","label":"cve@mitre.org"},{"url":"https://www.ruby-lang.org/en/news/2026/08/27/multiple-vulnerabilities-in-resolv/","label":"cve@mitre.org"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80212.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-80212"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2525066"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-80212"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80212"},{"url":"https://github.com/ruby/resolv/commit/6393c628b224d0234ef915813c0977e11ebe57ea"},{"url":"https://access.redhat.com/errata/RHSA-2026:57986"},{"url":"https://access.redhat.com/errata/RHSA-2026:57994"},{"url":"https://access.redhat.com/errata/RHSA-2026:57565"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.00569,"epssPercentile":0.45884,"ingestedAt":"2026-09-09T16:14:05.516Z","vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","affected":["lightspeed_core","enterprise_linux 10","enterprise_linux 6","enterprise_linux 7","enterprise_linux 8","enterprise_linux 9","hardened_images"],"patched":["hardened_images"],"slug":"CVE-2026-80212","body":"## Overview\n\nAn issue was discovered in the resolv gem before 0.7.2 for Ruby. Resolv::DNS::Resource.get_class, Resolv::DNS::Resource::Generic.create, and Resolv::DNS::SvcParam::Generic.create generate a new class for each unknown DNS resource record (type, class) pair, or each unknown SvcParamKey, encountered while decoding a response. Each generated class was permanently registered both as a constant on Resource (or SvcParam::Generic) and as an entry in a class-lookup hash (ClassHash), and thus the class remained reachable through that constant after the response was discarded. Type and class are each 16-bit values, and thus an attacker controlling DNS responses (a spoofed response, or a malicious or hijacked upstream DNS server) has roughly 2^32 distinct (type, class) pairs to choose from. A single response of a few hundred kilobytes carrying tens of thousands of distinct unknown types permanently grows process memory by tens of megabytes; repeated responses accumulate without bound and are never reclaimed by garbage collection, because the constant keeps each class alive. Any code path that calls Resolv::DNS::Message.decode on attacker-influenced DNS responses is affected. resolv is a default gem, and thus this is reachable from a plain Ruby installation without any additional dependency.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:57986** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:57986)\n- **RHSA-2026:57994** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:57994)\n- **RHSA-2026:57565** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:57565)\n- **Red Hat VEX** · Important · affected: Lightspeed Core, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Lightspeed Core, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, … · updated 2026-09-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80212.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}