CVE-2021-20291 — storage
MEDIUMCVE-2021-20291 is a medium-severity (CVSS 6.5) CWE-667 vulnerability in github.com/containers/storage. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/containers/storage — see the affected versions and patch details below.
Improper Locking in github.com/containers/storage
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-2021-20291 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
github.com/containers/storageReal-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
A deadlock vulnerability was found in 'github.com/containers/storage' in versions before 1.28.1. When a container image is processed, each layer is unpacked using tar. If one of those layers is not a valid tar archive this causes an error leading to an unexpected situation where the code indefinitely waits for the tar unpacked stream, which never finishes. An attacker could use this vulnerability to craft a malicious image, which when downloaded and stored by an application using containers/storage, would then cause a deadlock leading to a Denial of Service (DoS).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/containers/storage | all versions | 1.28.1go get github.com/containers/storage@v1.28.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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/storage, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/containers/storage to 1.28.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20291 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-2021-20291 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-20291. 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.
The vulnerability was first exposed in v1.23.8 of containers/storage (and subsequently fixed in v1.28.1) with this git commit [1]. * In OpenShift Container Platform (OCP) only 4.7 contains a version of CRI-O (and openshift/ose-docker-builder) which uses a vulnerable version of containers/storage. Subsequently this has…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | container-tools:3.0-8050020220104131412.e34216c9 | RHBA-2022:0348 |
| Red Hat Enterprise Linux 8 | container-tools:rhel8-8050020210921082437.faa19cc5 | RHSA-2021:4154 |
| Red Hat Enterprise Linux 9 | podman-2:4.2.0-3.el9 | RHSA-2022:7954 |
| Red Hat Enterprise Linux 9 | skopeo-2:1.9.2-1.el9 | RHSA-2022:7955 |
| Red Hat Enterprise Linux 9 | buildah-1:1.27.0-2.el9 | RHSA-2022:8008 |
| Red Hat OpenShift Container Platform 4.7 | cri-o-0:1.20.2-6.rhaos4.7.gitf1d5201.el7 | RHSA-2021:1150 |
| Red Hat OpenShift Container Platform 4.8 | atomic-openshift-service-idler-0:4.8.0-202106281541.p0.git.39cfc66.assembly.stream.el8 | RHSA-2021:2437 |
| Red Hat OpenShift Container Platform 4.8 | openshift4/ose-docker-builder:v4.8.0-202107152024.p0.git.70b7b95.assembly.stream | RHSA-2021:2438 |
Frequently Asked Questions
Is CVE-2021-20291 in your dependencies?
O3 Security finds CVE-2021-20291 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.