EUVD-2026-19788
GHSA-h27x-rffw-24p4
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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4Tags
Description
Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.3.0 to before 2.9.0, within the URI template implementation in Addressable, two classes of URI template generate regular expressions vulnerable to catastrophic backtracking. Templates using the * (explode) modifier with any expansion operator (e.g., {foo*}, {+var*}, {#var*}, {/var*}, {.var*}, {;var*}, {?var*}, {&var*}) generate patterns with nested unbounded quantifiers that are O(2^n) when matched against a maliciously crafted URI. Templates using multiple variables with the + or # operators (e.g., {+v1,v2,v3}) generate patterns with O(n^k) complexity due to the comma separator being within the matched character class, causing ambiguous backtracking across k variables. When matched against a maliciously crafted URI, this can result in catastrophic backtracking and uncontrolled resource consumption, leading to denial of service. This vulnerability is fixed in 2.9.0.
Analysis
Regular expression denial of service (ReDoS) in the Addressable Ruby library versions 2.3.0 through 2.8.x allows unauthenticated remote attackers to cause application-level denial of service through maliciously crafted URIs that trigger catastrophic backtracking in URI template expansion. The vulnerability affects URI templates using explode modifiers (e.g., {foo*}, {+var*}) and multi-variable templates with + or # operators (e.g., {+v1,v2,v3}), generating O(2^n) and O(n^k) complexity regex patterns respectively. …
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Remediation
Within 24 hours: Identify all applications and services using Addressable library versions 2.3.0 through 2.8.x via dependency audits (e.g., bundler, pip, or equivalent package managers). Within 7 days: Upgrade Addressable to version 2.9.0 or later across all affected systems; prioritize external-facing applications that process user-supplied URIs. …
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