Medium 6.9Published Mar 23, 2026

CVE-2026-33169Rails Active Support has a possible ReDoS vulnerability in number_to_delimited

Updated under an hour ago (Oct 27, 2026, 12:10 AM ET)

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It affects rails activesupport and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for rails activesupport

Exploited in the last 30 days

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.

CVSS: 6.9 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness (CWE): CWE-400, CWE-1333
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

rails activesupport rails:activesupport (from the name)	from 8.1.0.beta1, < 8.1.2.1; from 8.0.0.beta1, < 8.0.4.1; before 7.2.3.1	CNA record
rubyonrails rails rubyonrails:rails	before 7.2.3.1; from 8.0.0 before 8.0.4.1; from 8.1.0 before 8.1.2.1	NVD

References

References

https://github.com/rails/rails/security/advisories/GHSA-cg4j-q9v8-6v38	x-refsource-confirm, vendor-advisory
https://github.com/rails/rails/commit/29154f1097da13d48fdb3200760b3e3da66dcb11	x-refsource-misc, patch
https://github.com/rails/rails/commit/b54a4b373c6f042cab6ee2033246b1c9ecc38974	x-refsource-misc, patch
https://github.com/rails/rails/commit/ec1a0e215efd27a3b3911aae6df978a80f456a49	x-refsource-misc, patch
https://github.com/rails/rails/releases/tag/v7.2.3.1	x-refsource-misc, release-notes
https://github.com/rails/rails/releases/tag/v8.0.4.1	x-refsource-misc, release-notes
https://github.com/rails/rails/releases/tag/v8.1.2.1	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.