GHSA-h27x-rffw-24p4
HIGHGHSA-h27x-rffw-24p4 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in addressable. O3 Security confirms whether GHSA-h27x-rffw-24p4 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Addressable has a Regular Expression Denial of Service in Addressable templates
Blast Radius
addressableReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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. The first pattern was partially addressed in 2.8.10 for certain operator combinations. Both patterns are fully remediated in 2.9.0.
Users of the URI parsing capabilities in Addressable but not the URI template matching capabilities 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). It was partially fixed in version 2.8.10 and fully remediated in 2.9.0.
The vulnerability is more exploitable on MRI Ruby < 3.2 and on all versions of JRuby and TruffleRuby. MRI Ruby 3.2 and later ship with Onigmo 6.9, which introduces memoization that prevents catastrophic backtracking for the first class of template. JRuby and TruffleRuby do not implement equivalent memoization and remain vulnerable to all patterns.
This has been confirmed on the following runtimes:
| Runtime | Status |
|---|---|
| MRI Ruby 2.6 | Vulnerable |
| MRI Ruby 2.7 | Vulnerable |
| MRI Ruby 3.0 | Vulnerable |
| MRI Ruby 3.1 | Vulnerable |
| MRI Ruby 3.2 | Partially vulnerable |
| MRI Ruby 3.3 | Partially vulnerable |
| MRI Ruby 3.4 | Partially vulnerable |
| MRI Ruby 4.0 | Partially vulnerable |
| JRuby 10.0 | Vulnerable |
| TruffleRuby 21.2 | Vulnerable |
Workarounds
-
Upgrade to MRI Ruby 3.2 or later, if your application does not use JRuby or TruffleRuby. The Onigmo memoization introduced in MRI Ruby 3.2 prevents catastrophic backtracking from nested unbounded quantifiers (pattern 1 above — templates using the
*modifier). It does not reliably mitigate the O(n^k) multi-variable case (pattern 2), so upgrading Ruby alone may not be sufficient if your templates use{+v1,v2,...}or{#v1,v2,...}syntax. -
Avoid using vulnerable template patterns when matching user-supplied input on unpatched versions of the library:
- Templates using the
*(explode) modifier:{foo*},{+var*},{#var*},{.var*},{/var*},{;var*},{?var*},{&var*} - Templates using multiple variables with the
+or#operators:{+v1,v2},{#v1,v2,v3}, etc.
- Templates using the
-
Apply a short timeout around any call to
Template#matchorTemplate#extractthat processes user-supplied data.
References
- https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS
- https://cwe.mitre.org/data/definitions/1333.html
- https://www.regular-expressions.info/catastrophic.html
Credits
Discovered in collaboration with @jamfish.
For more information
If you have any questions or comments about this advisory:
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | addressable | ≥ 2.3.0&&< 2.9.0 | 2.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for addressable. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update addressable to 2.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h27x-rffw-24p4 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-h27x-rffw-24p4 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-h27x-rffw-24p4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-h27x-rffw-24p4 in your dependencies?
O3 detects GHSA-h27x-rffw-24p4 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.