CVE-2021-31525 — net
MEDIUMCVE-2021-31525 is a medium-severity (CVSS 5.9) CWE-674 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/http/httpguts vulnerable to Uncontrolled Recursion
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-2021-31525 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 378,567 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
net/http in Go before 1.15.12 and 1.16.x before 1.16.4 allows remote attackers to cause a denial of service (panic) via a large header to ReadRequest or ReadResponse. Server, Transport, and Client can each be affected in some configurations.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/net | all versions | 0.0.0-20210428140749-89ef3d95e781go get golang.org/x/net@v0.0.0-20210428140749-89ef3d95e781 |
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 0.0.0-20210428140749-89ef3d95e781 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-31525 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-2021-31525 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-31525. 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.
This vulnerability potentially affects any component written in Go that uses net/http from the standard library. In OpenShift Container Platform (OCP), OpenShift Virtualization, OpenShift ServiceMesh (OSSM) and OpenShift distributed tracing (formerly OpenShift Jaeger), no server side component allows HTTP header…
| Product | Fixed in | Advisory |
|---|---|---|
| Native Client for RHEL 7 for Red Hat Storage | heketi-0:10.4.0-2.el7rhgs | RHSA-2022:0308 |
| Openshift Serveless 1.16 | openshift-serverless-1/client-kn-rhel8:0.22.0-4 | RHSA-2021:2705 |
| Openshift Serverless 1.17 | openshift-serverless-1/client-kn-rhel8:0.23.2-2 | RHSA-2021:3556 |
| Openshift Serverless 1 on RHEL 8 | openshift-serverless-clients-0:0.22.0-3.el8 | RHSA-2021:2704 |
| Openshift Serverless 1 on RHEL 8 | openshift-serverless-clients-0:0.23.2-1.el8 | RHSA-2021:3555 |
| Red Hat Enterprise Linux 8 | go-toolset:rhel8-8040020210716085908.5081a262 | RHSA-2021:3076 |
| Red Hat Gluster Storage 3.5 for RHEL 7 | rhgs3/rhgs-gluster-block-prov-rhel7:3.11.8-1 | RHSA-2021:3748 |
| Red Hat Migration Toolkit for Containers 1.4 | rhmtc/openshift-migration-controller-rhel8:v1.4.6-4 | RHBA-2021:2854 |
Frequently Asked Questions
Is CVE-2021-31525 in your dependencies?
O3 Security finds CVE-2021-31525 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.