Microsoft Security Response Center guidance
Vendor revision: Nov 14, 2026Release Notes
Vulnerability intelligence
CVE-2026-126351 and is rated Medium severity with a CVSS score of 5.9. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
Release Notes
Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. Prior to 2.9.1, Addressable::URI.normalize_path repeatedly scans and rewrites paths while removing only one nested dot segment per pass, producing quadratic work.
URI#normalize, URI#normalized_path, URI#join, URI#==, and URI#=== inherit the behavior, so processing a sufficiently long attacker-controlled URI can consume a worker thread and cause denial of service on every Ruby implementation. URI.parse alone and code that never normalizes, compares, or joins untrusted URIs are unaffected.
This issue is fixed in version 2.9.1.
Source: NVD