CVE-2026-35611
HIGHCVE-2026-35611 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in addressable. O3 Security confirms whether CVE-2026-35611 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
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
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
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.
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 CVE-2026-35611 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 CVE-2026-35611 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 CVE-2026-35611. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-35611 in your dependencies?
O3 detects CVE-2026-35611 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.