CVE-2021-32740 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in addressable. A fix is available for addressable — see the affected versions and patch details below.
Regular Expression Denial of Service in Addressable templates
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-32740 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
addressableReal-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
Impact
Within the URI template implementation in Addressable, a maliciously crafted template may result in uncontrolled resource consumption, leading to denial of service when matched against a URI. In typical usage, templates would not normally be read from untrusted user input, but nonetheless, no previous security advisory for Addressable has cautioned against doing this. Users of the parsing capabilities in Addressable but not the URI template capabilities are unaffected.
Patches
The vulnerability was introduced in version 2.3.0 (previously yanked) and has been present in all subsequent versions up to, and including, 2.7.0. It is fixed in version 2.8.0.
Workarounds
The vulnerability can be avoided by only creating Template objects from trusted sources that have been validated not to produce catastrophic backtracking.
References
- https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS
- https://cwe.mitre.org/data/definitions/1333.html
- https://www.regular-expressions.info/catastrophic.html
For more information
If you have any questions or comments about this advisory:
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | addressable | ≥ 2.3.0&&< 2.8.0 | 2.8.0bundle update addressable --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for addressable, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update addressable to 2.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32740 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-32740 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-32740. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Red Hat CloudForms 5.0 (CFME 5.11) is in the maintenance support phase and we are no longer fixing Moderate/Low severity security bugs. Reference: https://access.redhat.com/support/policy/updates/cloudforms OpenShift 3.11 components are currently in maintenance support phase, hence Moderate/Low severity security bugs…
| Product | Fixed in | Advisory |
|---|---|---|
| OpenShift Logging 5.2 | openshift-logging/fluentd-rhel8:v5.2.0-10 | RHBA-2021:3393 |
| Red Hat Satellite 6.10 for RHEL 7 | tfm-rubygem-addressable-0:2.8.0-1.el7sat | RHSA-2021:4702 |
Frequently Asked Questions
Is CVE-2021-32740 in your dependencies?
O3 Security finds CVE-2021-32740 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.