CVE-2021-33194 is a high-severity (CVSS 7.5) CWE-835 vulnerability in golang.org/x/net. A fix is available for golang.org/x/net — see the affected versions and patch details below.
golang.org/x/net/html Infinite Loop vulnerability
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-2021-33194 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 379,145 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
golang.org/x/netReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
golang.org/x/net before v0.0.0-20210520170846-37e1c6afe023 allows attackers to cause a denial of service (infinite loop) via crafted ParseFragment input.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/net | all versions | 0.0.0-20210520170846-37e1c6afe023go get golang.org/x/net@v0.0.0-20210520170846-37e1c6afe023 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/net, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update golang.org/x/net to 0.0.0-20210520170846-37e1c6afe023 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-33194 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-2021-33194 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-33194. 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 Developer Tools go-toolset-1.14-golang not affected because the vulnerable code is not shipped. This vulnerability within golang and buildah shipped with RHEL-7 are out of support scope. For more information on Red Hat's support scope, visit: https://access.redhat.com/support/policy/updates/errata For RHEL-8's…
| Product | Fixed in | Advisory |
|---|---|---|
| OpenShift Logging 5.3 | openshift-logging/elasticsearch-proxy-rhel8:v1.0.0-44 | RHSA-2021:4627 |
| Red Hat OpenShift Container Platform 4.8 | openshift4/ose-cluster-node-tuning-operator:v4.8.0-202107091725.p0.git.6be3f67.assembly.stream | RHSA-2021:2438 |
| Red Hat OpenShift Container Platform 4.9 | openshift4/ose-oauth-proxy:v4.9.0-202109302016.p0.git.9ea1ebc.assembly.stream | RHSA-2021:3759 |
Frequently Asked Questions
Is CVE-2021-33194 in your dependencies?
O3 Security finds CVE-2021-33194 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.