Resource exhaustion in Rails Activesupport
CVE-2026-33169
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.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.006 (46.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 46.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.006 · change: +0.001
Affected products
- Rails Activesupport — versions >= 8.1.0.beta1, < 8.1.2.1, >= 8.0.0.beta1, < 8.0.4.1, < 7.2.3.1
- Rubyonrails Rails
Weakness classification (CWE)
References
- github.com/rails/rails/security/advisories/GHSA-cg4j-q9v8-6v38 (Vendor Advisory)
- github.com/rails/rails/commit/29154f1097da13d48fdb3200760b3e3da66dcb11 (Patch)
- github.com/rails/rails/commit/b54a4b373c6f042cab6ee2033246b1c9ecc38974 (Patch)
- github.com/rails/rails/commit/ec1a0e215efd27a3b3911aae6df978a80f456a49 (Patch)
- github.com/rails/rails/releases/tag/v7.2.3.1 (Release Notes)
- github.com/rails/rails/releases/tag/v8.0.4.1 (Release Notes)
- github.com/rails/rails/releases/tag/v8.1.2.1 (Release Notes)
Frequently asked questions
- What is CVE-2026-33169?
- CVE-2026-33169 is a medium-severity vulnerability in Rails Activesupport, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-03-24.
- How severe is CVE-2026-33169?
- Medium severity. CVSS v3 base score is 5.3 out of 10.