What’s Vulnerable › Vulnerabilities

CVE-2026-33176: Rails Active Support has a possible DoS vulnerability in its number helpers

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-24 · updated 2026-06-17
• Weakness: CWE-400

Description

Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, Active Support number helpers accept strings containing scientific notation (e.g. `1e10000`), which `BigDecimal` expands into extremely large decimal representations. This can cause excessive memory allocation and CPU consumption when the expanded number is formatted, possibly resulting in a DoS vulnerability. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

Affected products

• Ruby on Rails: before 7.2.3.1; from 8.0.0 before 8.0.4.1; from 8.1.0 before 8.1.2.1 — fixed in 7.2.3.1, 8.0.4.1, 8.1.2.1
• Rubygems Activesupport: from 8.1.0.beta1 before 8.1.2.1; from 8.0.0.beta1 before 8.0.4.1; before 7.2.3.1; 8.1.0, 8.1.0.beta1, 8.1.0.rc1, 8.1.1, 8.1.2, 8.0.0 (+491) — fixed in 8.1.2.1, 8.0.4.1, 7.2.3.1

How to fix

Upgrade to a fixed version: Ruby on Rails 7.2.3.1, 8.0.4.1, 8.1.2.1; Rubygems Activesupport 8.1.2.1, 8.0.4.1, 7.2.3.1. Check the vendor advisory for mitigations.

References

• https://github.com/rails/rails/commit/19dbab51ca086a657bb86458042bc44314916bcb
• https://github.com/rails/rails/commit/ebd6be18120d1136511eb516338e27af25ac0a1a
• https://github.com/rails/rails/commit/ee2c59e730e5b8faed502cd2c573109df093f856
• https://github.com/rails/rails/releases/tag/v7.2.3.1
• https://github.com/rails/rails/releases/tag/v8.0.4.1
• https://github.com/rails/rails/releases/tag/v8.1.2.1
• https://github.com/rails/rails/security/advisories/GHSA-2j26-frm8-cmj9

Get alerted when CVE-2026-33176 or the next vulnerability affects your stack