CVE-2026-33169
Fix: rails/rails@29154f1CVE-2026-33169 is a Uncontrolled Resource Consumption vulnerability in activesupport. O3 Security confirms whether CVE-2026-33169 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Rails Active Support has a possible ReDoS vulnerability in number_to_delimited
Real-World Exposure
activesupport💎activesupport💎activesupportReal-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
Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. NumberToDelimitedConverter uses a lookahead-based regular expression with gsub! to insert thousands delimiters. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, the interaction between the repeated lookahead group and gsub! can produce quadratic time complexity on long digit strings. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | activesupport | ≥ 8.1.0.beta1&&< 8.1.2.1 | 8.1.2.1 |
| 💎RubyGems | activesupport | ≥ 8.0.0.beta1&&< 8.0.4.1 | 8.0.4.1 |
| 💎RubyGems | activesupport | all versions | 7.2.3.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for activesupport. 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 activesupport to 8.1.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33169 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-2026-33169 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-2026-33169. 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-2026-33169 in your dependencies?
O3 detects CVE-2026-33169 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.