CVE-2026-80212

CVE Details

Release Date:	2026-08-27
Impact:	Important	What is this?

Description

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 (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.

See more information about CVE-2026-80212 from MITRE CVE dictionary and NIST NVD

NOTE: The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 metrics

Base Score:	7.5
Vector String:	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Version:	3.1
Attack Vector:	Network
Attack Complexity:	Low
Privileges Required:	None
User Interaction:	None
Scope:	Unchanged
Confidentiality Impact:	None
Integrity Impact:	None
Availability Impact:	High

Errata information

Platform	Errata	Release Date
Oracle Linux version 10 (ruby)	ELSA-2026-72785	2026-09-28
Oracle Linux version 10 (ruby4.0)	ELSA-2026-72427	2026-09-28
Oracle Linux version 9 (ruby)	ELSA-2026-72484	2026-09-29
Oracle Linux version 9 (ruby)	ELSA-2026-72485	2026-09-29
Oracle Linux version 9 (rubygem-mysql2)	ELSA-2026-72484	2026-09-29
Oracle Linux version 9 (rubygem-mysql2)	ELSA-2026-72485	2026-09-29
Oracle Linux version 9 (rubygem-pg)	ELSA-2026-72484	2026-09-29
Oracle Linux version 9 (rubygem-pg)	ELSA-2026-72485	2026-09-29