CVE-2021-3121 is a high-severity (CVSS 8.6) CWE-129 vulnerability in github.com/gogo/protobuf. A fix is available for github.com/gogo/protobuf — see the affected versions and patch details below.
Improper Input Validation in GoGo Protobuf
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-2021-3121 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
github.com/gogo/protobufReal-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
An issue was discovered in GoGo Protobuf before 1.3.2. plugin/unmarshal/unmarshal.go lacks certain index validation, aka the "skippy peanut butter" issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gogo/protobuf | all versions | 1.3.2go get github.com/gogo/protobuf@v1.3.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gogo/protobuf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/gogo/protobuf to 1.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3121 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-2021-3121 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-3121. 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.
OpenShift Container Platform (OCP), OpenShift ServiceMesh (OSSM) and Red Hat OpenShift Jaeger (RHOSJ) all include code generated by github.com/gogo/protobuf to parse protobuf messages. However, no component is known to accept protobuf messages from unauthenticated sources, hence this vulnerability is rated Moderate…
| Product | Fixed in | Advisory |
|---|---|---|
| AMQ Broker 7.10.1 | amq-broker-operator-container | RHSA-2022:6916 |
| Cryostat 2 on RHEL 8 | cryostat-20-tech-preview/cryostat-grafana-dashboard-rhel8:2.1.0-1 | RHSA-2022:1679 |
| OpenShift Logging 5.0 | openshift-logging/cluster-logging-rhel8-operator:v5.0.4-5 | RHSA-2021:2136 |
| OpenShift Logging 5.0 | openshift-logging/elasticsearch-proxy-rhel8:v5.0.5-5 | RHSA-2021:2374 |
| OpenShift Service Mesh 2.0 | kiali-0:v1.24.7.redhat1-1.el8 | RHSA-2022:1276 |
| Red Hat Advanced Cluster Management for Kubernetes 2.0 for RHEL 8 | rhacm2/acm-operator-bundle:v2.0.8-7 | RHSA-2021:0719 |
| Red Hat Advanced Cluster Management for Kubernetes 2.1 for RHEL 8 | rhacm2/acm-must-gather-rhel8:v2.1.3-3 | RHSA-2021:0607 |
| Red Hat OpenShift Container Platform 4.10 | openshift4/ose-csi-driver-manila-rhel8-operator:v4.10.0-202202160023.p0.g16f67d6.assembly.stream | RHSA-2022:0056 |
Frequently Asked Questions
Is CVE-2021-3121 in your dependencies?
O3 Security finds CVE-2021-3121 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.