CVE-2020-25613 is a high-severity (CVSS 7.5) CWE-444 vulnerability in webrick. A fix is available for webrick — see the affected versions and patch details below.
WEBRick vulnerable to HTTP Request/Response Smuggling
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-2020-25613 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 377,166 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
webrick💎webrick💎webrickReal-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
An issue was discovered in Ruby through 2.5.8, 2.6.x through 2.6.6, and 2.7.x through 2.7.1. WEBrick, a simple HTTP server bundled with Ruby, had not checked the transfer-encoding header value rigorously. An attacker may potentially exploit this issue to bypass a reverse proxy (which also has a poor header check), which may lead to an HTTP Request Smuggling attack.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | webrick | ≥ 1.6.0&&< 1.6.1 | 1.6.1bundle update webrick --conservative |
| 💎RubyGems | webrick | ≥ 1.5.0&&< 1.5.1 | 1.5.1bundle update webrick --conservative |
| 💎RubyGems | webrick | all versions | 1.4.4bundle update webrick --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for webrick, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update webrick to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-25613 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-2020-25613 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-25613. 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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | ruby:2.7-8040020210421133318.522a0ee4 | RHSA-2021:2584 |
| Red Hat Enterprise Linux 8 | ruby:2.5-8040020200923213910.522a0ee4 | RHSA-2021:2587 |
| Red Hat Enterprise Linux 8 | ruby:2.6-8040020210430142949.522a0ee4 | RHSA-2021:2588 |
| 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 Software Collections for Red Hat Enterprise Linux 7 | rh-ruby25-ruby-0:2.5.9-9.el7 | RHSA-2021:2104 |
| Red Hat Software Collections for Red Hat Enterprise Linux 7 | rh-ruby27-ruby-0:2.7.3-129.el7 | RHSA-2021:2229 |
| Red Hat Software Collections for Red Hat Enterprise Linux 7 | rh-ruby26-ruby-0:2.6.7-119.el7 | RHSA-2021:2230 |
Frequently Asked Questions
Is CVE-2020-25613 in your dependencies?
O3 Security finds CVE-2020-25613 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.