Regular expression denial of service vulnerability (ReDoS) in date

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2021-41817: 3.46% estimated exploitation activity in the next 30 days; percentile 89.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Date’s parsing methods including Date.parse are using Regexps internally, some of which are vulnerable against regular expression denial of service. Applications and libraries that apply such methods to untrusted input may be affected. The fix limits the input length up to 128 bytes by default instead of changing the regexps. This is because Date gem uses many Regexps and it is possible that there are still undiscovered vulnerable Regexps. For compatibility, it is allowed to remove the limitation by explicitly passing limit keywords as nil like Date.parse(str, limit: nil), but note that it may take a long time to parse. Please update the date gem to version 3.2.1, 3.1.2, 3.0.2, and 2.0.1, or later. You can use gem update date to update it. If you are using bundler, please add gem "date", "= 3.2.1" to your Gemfile. If you import date from the standard library rather than as a gem you should update your Ruby install to 3.0.3, 2.7.5, 2.6.9 or later. Users unable to upgrade may consider…

Published by the source

16 Nov 2021, 00:32 UTC

Last modified by the source

24 Jan 2024, 19:18 UTC

Source last checked

26 Oct 2026, 15:48 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qg54-694p-wgpp

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# Patch Next advisory brief: CVE-2021-41817

Advisory: Regular expression denial of service vulnerability (ReDoS) in date
IDs: CVE-2021-41817, GHSA-qg54-694p-wgpp
Record: https://patchnext.com/advisories/cve-2021-41817 (revision 1, source checked 26 Oct 2026, 15:48 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: date 3.2.1, 3.1.2, 3.0.2, 2.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems date: affected >= 3.2.0, < 3.2.1; >= 3.1.0, < 3.1.2; >= 3.0.0, < 3.0.2; < 2.0.1; fixed in 3.2.1, 2.0.1, 3.0.2, 3.1.2

## Suggested inspection (read-only)
- RubyGems date: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on date.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-qg54-694p-wgpp (GitHub-reviewed advisory GHSA-qg54-694p-wgpp lists affected ranges: RubyGems date >=3.2.0 =3.1.0 =3.0.0 =0 <2.0.1)

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