PatchTheCVECVE-2021-41817: Date.parse in the date gem through 3.2.0 for Ruby allows ReDoS (regular expression Denial of Service) via a lo
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HIGH 7.5REMOTEWATCHLISTUPGRADEUPGRADEMITIGATE
CVE-2021-41817 is a high-severity flaw (CVSS 7.5) affecting date, ruby, software collections. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Date.parse in the date gem through 3.2.0 for Ruby allows ReDoS (regular expression Denial of Service) via a long string. The fixed versions are 3.2.1, 3.1.2, 3.0.2, and 2.0.1.
Why this priority
- High severity
- Public exploit reference
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 3.5% (top 11%) |
| CISA exploited list | No |
| Weakness | CWE-1333 |
| Published | 2022-01-01 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
ruby-lang date UPGRADE
Affected: < 2.0.1 · >= 3.0.0 and < 3.0.2 · >= 3.1.0 and < 3.1.2 · 3.2.0
Fixed in: 2.0.1, 3.0.2, 3.1.2
Safe to downgrade to: a release before 3.0.0
1. Check installed version
apt-cache policy date || rpm -q date || date --version
2. UPGRADE to 2.0.1 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade date
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade date
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)
apt-cache madison date
sudo apt install date=<VERSION_BEFORE_3.0.0>
sudo apt-mark hold date
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list date
sudo dnf downgrade date-<VERSION_BEFORE_3.0.0>
sudo dnf versionlock add date
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
ruby-lang ruby UPGRADE
Affected: >= 2.6.0 and < 2.6.9 · >= 2.7.0 and < 2.7.5 · >= 3.0.0 and < 3.0.3
Fixed in: 2.6.9, 2.7.5, 3.0.3
Safe to downgrade to: a release before 2.6.0
1. Check installed version
apt-cache policy ruby || rpm -q ruby || ruby --version
2. UPGRADE to 2.6.9 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade ruby
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade ruby
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 2.6.0 (Debian / Ubuntu)
apt-cache madison ruby
sudo apt install ruby=<VERSION_BEFORE_2.6.0>
sudo apt-mark hold ruby
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list ruby
sudo dnf downgrade ruby-<VERSION_BEFORE_2.6.0>
sudo dnf versionlock add ruby
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
redhat software collections MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy software-collections || rpm -q software-collections || software-collections --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
redhat enterprise linux MITIGATE
Affected: 7.0 · 8.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
fedoraproject fedora MITIGATE
Affected: 34 · 35
Fixed in: no fixed release known
Safe to downgrade to: a release before 34
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
debian debian linux MITIGATE
Affected: 9.0 · 10.0 · 11.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 9.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-41817?
date: upgrade to 2.0.1, 3.0.2, 3.1.2; ruby: upgrade to 2.6.9, 2.7.5, 3.0.3; software collections: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-41817 being exploited?
CVE-2021-41817 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-41817 affect?
CVE-2021-41817 affects date, ruby, software collections. Severity is high (CVSS 7.5). Date.parse in the date gem through 3.2.0 for Ruby allows ReDoS (regular expression Denial of Service) via a long string. The fixed versions are 3.2.1, 3.1.2, 3.0.2, and 2.0.1.
How urgent is CVE-2021-41817?
Priority 64/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist
Software pages
Debian vulnerabilities · Ruby vulnerabilities