CVE-2021-41817 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in date. 1 public exploit reference exists, so weaponization risk is real. A fix is available for date — see the affected versions and patch details below.
Regular expression denial of service vulnerability (ReDoS) in date
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41817 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
date💎date💎date💎dateReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
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 using Date.strptime instead with a predefined date format
Date.strptime('2001-02-20', '%Y-%m-%d')
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | date | ≥ 3.2.0&&< 3.2.1 | 3.2.1bundle update date --conservative |
| 💎RubyGems | date | ≥ 3.1.0&&< 3.1.2 | 3.1.2bundle update date --conservative |
| 💎RubyGems | date | ≥ 3.0.0&&< 3.0.2 | 3.0.2bundle update date --conservative |
| 💎RubyGems | date | all versions | 2.0.1bundle update date --conservative |
Affected Products
debian linuxdebianfedorafedoraprojectfactoryopensuseleapopensuseenterprise linuxredhatsoftware collectionsredhatResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for date, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update date to 3.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41817 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | ruby:2.6-8050020211215144356.c5368500 | RHSA-2022:0543 |
| Red Hat Enterprise Linux 8 | ruby:2.5-8060020220715152618.ad008a3a | RHSA-2022:5779 |
| Red Hat Enterprise Linux 8 | ruby:2.7-8060020220728151401.ad008a3a | RHSA-2022:6447 |
| Red Hat Enterprise Linux 8 | ruby:3.0-8060020220810162001.ad008a3a | RHSA-2022:6450 |
| Red Hat Enterprise Linux 8.1 Update Services for SAP Solutions | ruby:2.6-8010020220201152941.c27ad7f8 | RHSA-2022:0581 |
| Red Hat Enterprise Linux 8.2 Extended Update Support | ruby:2.6-8020020220201131207.4cda2c84 | RHSA-2022:0582 |
| Red Hat Enterprise Linux 8.4 Extended Update Support | ruby:2.6-8040020220131135901.522a0ee4 | RHSA-2022:0544 |
| Red Hat Software Collections for Red Hat Enterprise Linux 7 | rh-ruby26-ruby-0:2.6.9-120.el7 | RHSA-2022:0708 |
Frequently Asked Questions
Is CVE-2021-41817 in your dependencies?
Find it across RubyGems, including transitive dependencies.