ADDRESSABLE · CVE-2026-126350 · Package
FIX → 2.9.1
Addressable's URI template matching builds regular expressions that backtrack catastrophically when a crafted URI starts with the operator character of an exploded expression. An input under 60 bytes can tie up a thread for minutes, which is a denial of service.
first public Oct 30, 2026 · 2 sources
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Applications that use Addressable's URI template match or extract methods on user-supplied URIs, with templates that use the explode modifier and the /, ., ;, ?, or & operators, running on MRI Ruby below 3.2 or on JRuby. Applications that only parse URIs or only call Template#expand are unaffected, and so are those on MRI 3.2 or later or TruffleRuby 40.0.
Not affected if ruby-3.2-or-later, template-expand-only, truffleruby, uri-parsing-only
Who cares addressable, ruby, rubygems
bundle exec gem list addressable or inspect Gemfile.lock for addressable, looking for a version at or above 2.3.2 and below 2.9.1.ruby -v; the flaw applies to MRI Ruby below 3.2 and to JRuby, not to MRI 3.2+ or TruffleRuby 40.0.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.
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Template#match or Template#extract called on user-supplied input with templates using * with /, ., ;, ? or & operators.Upgrade to 2.9.1
addressable 2.9.1Users of the URI parsing capabilities in Addressable but not the URI template matching capabilities are unaffected. Users who only call Template#expand are unaffected.
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 3.3 | Not affected |
| MRI Ruby 3.4 | Not affected |
| MRI Ruby 4.0 | Not affected |
| JRuby 9.4 | Vulnerable |
| TruffleRuby 40.0 | Not affected |
* modifier with the /, ., ;, ? or & operators.Template#match or Template#extract that processes user-supplied data.Reported independently by @ebenoist, @andrewstellman, and then @halogenandtoast.
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