CVE-2020-7663 is a high-severity (CVSS 7.5) vulnerability in websocket-extensions. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2020-7663 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Regular Expression Denial of Service in websocket-extensions (RubyGem)
Real-World Exposure
websocket-extensionsReal-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
websocket-extensions ruby module prior to 0.1.5 allows Denial of Service (DoS) via Regex Backtracking. The extension parser may take quadratic time when parsing a header containing an unclosed string parameter value whose content is a repeating two-byte sequence of a backslash and some other character. This could be abused by an attacker to conduct Regex Denial Of Service (ReDoS) on a single-threaded server by providing a malicious payload with the Sec-WebSocket-Extensions header.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | websocket-extensions | all versions | 0.1.5 |
Research 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 websocket-extensions. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update websocket-extensions to 0.1.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-7663 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 pinpoints whether CVE-2020-7663 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2020-7663. 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 4.7 (CFME 5.10) is in the maintenance phase and we will not be fixing Medium/Low impact security bugs. Reference: https://access.redhat.com/support/policy/updates/cloudforms Red Hat Satellite 6 ships affected RubyGem Websocket-extensions, however, product is not vulnerable to the flaw. A future…
Frequently Asked Questions
Is CVE-2020-7663 in your dependencies?
O3 detects CVE-2020-7663 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.