CVE-2026-126350

### Impact Within the URI template implementation in Addressable, templates using the `*` (explode) modifier with the `/`, `.`, `;`, `?` or `&` operators (e.g., `{/segments*}`, `{.ext*}`, `{;params*}`, `{?query*}`) generate regular expressions vulnerable to catastrophic backtracking. When `Template#match` or `Template#extract` is called with a maliciously crafted URI that starts with the operator's leading character, matching takes exponential time, leading to uncontrolled resource consumption and denial of service. An input under 60 bytes is enough to occupy a thread for minutes. GHSA-h27x-rffw-24p4 (CVE-2026-35611) reported this pattern as fully remediated in 2.9.0. The 2.9.0 fix only made the joiner between exploded members mandatory for templates without an operator, and its regression specs used inputs that never start with the operator's leading character, so the vulnerable part of the expression was never reached. This issue was originally reported in #364 by @ebenoist in 2019 but insufficiently investigated. Users of the URI parsing capabilities in Addressable but not the URI template matching capabilities are unaffected. Users who only call `Template#expand` are unaffected. ### Affected Versions This vulnerability affects Addressable >= 2.3.0 (note: 2.3.0 and 2.3.1 were yanked; the earliest installable release is 2.3.2), including 2.9.0. It is fixed in 2.9.1. The vulnerability is only exploitable on Ruby implementations whose regular expression engine backtracks without memoization: MRI Ruby < 3.2 and JRuby. MRI Ruby 3.2 and later are not affected: their regular expression engine memoizes backtracking, so these patterns still match in linear time. TruffleRuby 40.0 is not affected either. Earlier TruffleRuby versions were not tested. This has been confirmed on the following runtimes with Addressable 2.9.0: | Runtime | Status | |---------|--------| | MRI Ruby 2.7 | Vulnerable | | MRI Ruby 3.1 | Vulnerable | | MRI Ruby 3.2 | Not affected | | MRI Ruby 3