CVE-2021-3602 is a medium-severity (CVSS 5.5) Information Exposure vulnerability in github.com/containers/buildah. A fix is available for github.com/containers/buildah — see the affected versions and patch details below.
Buildah processes using chroot isolation may leak environment values to intermediate processes
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-2021-3602 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 377,238 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/containers/buildah🐹github.com/containers/buildah🐹github.com/containers/buildah🐹github.com/containers/buildahReal-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 information disclosure flaw was found in Buildah, when building containers using chroot isolation. Running processes in container builds (e.g. Dockerfile RUN commands) can access environment variables from parent and grandparent processes. When run in a container in a CI/CD environment, environment variables may include sensitive information that was shared with the container in order to be used only by Buildah itself (e.g. container registry credentials).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/containers/buildah | all versions | 1.16.8go get github.com/containers/buildah@v1.16.8 |
| 🐹Go | github.com/containers/buildah | ≥ 1.17.0&&< 1.17.2 | 1.17.2go get github.com/containers/buildah@v1.17.2 |
| 🐹Go | github.com/containers/buildah | ≥ 1.18.0&&< 1.19.9 | 1.19.9go get github.com/containers/buildah@v1.19.9 |
| 🐹Go | github.com/containers/buildah | ≥ 1.20.0&&< 1.21.3 | 1.21.3go get github.com/containers/buildah@v1.21.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/containers/buildah, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/containers/buildah to 1.16.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3602 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-2021-3602 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-3602. 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 4's builder container is not vulnerable to this flaw as it uses OCI isolation (i.e. using runc) and does not use chroot isolation.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | container-tools:rhel8-8050020210921082437.faa19cc5 | RHSA-2021:4154 |
| Red Hat Enterprise Linux 8 | container-tools:2.0-8050020210817115648.faa19cc5 | RHSA-2021:4221 |
| Red Hat Enterprise Linux 8 | container-tools:3.0-8050020210915114620.faa19cc5 | RHSA-2021:4222 |
Frequently Asked Questions
Is CVE-2021-3602 in your dependencies?
O3 Security finds CVE-2021-3602 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.