# Rails Active Support has a possible ReDoS vulnerability in number_to_delimited

Advisory record · `GHSA-cg4j-q9v8-6v38`

- **Identifiers:** `GHSA-cg4j-q9v8-6v38` · `CVE-2026-33169`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 23 Mar 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 23 Mar 2026, 20:52 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `activesupport` (RubyGems): affected `>=8.1.0.beta1, <8.1.2.1 || >=8.0.0.beta1, <8.0.4.1 || <7.2.3.1`; fixed in `8.1.2.1`, `8.0.4.1`, `7.2.3.1`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.9 Medium, CVSS 4.0: `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`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0066, the 51st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:16 UTC: First seen by agentprime
- 31 Oct 2026, 15:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-cg4j-q9v8-6v38)

## Sources

- [GitHub Advisory Database: GHSA-cg4j-q9v8-6v38](https://github.com/advisories/GHSA-cg4j-q9v8-6v38)
- [OSV: GHSA-cg4j-q9v8-6v38](https://osv.dev/vulnerability/GHSA-cg4j-q9v8-6v38)
- <https://github.com/rails/rails/security/advisories/GHSA-cg4j-q9v8-6v38>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-33169>
- <https://github.com/rails/rails/commit/29154f1097da13d48fdb3200760b3e3da66dcb11>
- <https://github.com/rails/rails/commit/b54a4b373c6f042cab6ee2033246b1c9ecc38974>
- <https://github.com/rails/rails/commit/ec1a0e215efd27a3b3911aae6df978a80f456a49>
- <https://github.com/rails/rails>
- <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/rubysec/ruby-advisory-db/blob/master/gems/activesupport/CVE-2026-33169.yml>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-cg4j-q9v8-6v38>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-cg4j-q9v8-6v38/>. Everything for agents: <https://agentprime.io/llms.txt>.