How severe is CVE-2019-19921?

CVE-2019-19921 has a CVSS score of 7/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2019-19921?

CVE-2019-19921 affects the following packages: github.com/opencontainers/runc (Go). Ecosystems affected: Go.

How do I fix CVE-2019-19921?

Update github.com/opencontainers/runc to 1.0.0-rc9.0.20200122160610-2fc03cc11c77 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-19921 is resolved across your whole dependency graph.

How do I detect CVE-2019-19921 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/opencontainers/runc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-19921 if there is no patch (or I can't update yet)?

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.

Is CVE-2019-19921 actively exploited in the wild?

No public exploit code has been indexed for CVE-2019-19921 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2019-19921?

CVE-2019-19921 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 36th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-19921?

CVE-2019-19921 is classified as CWE-706 (CWE-706). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2019-19921 published, and has it been updated?

CVE-2019-19921 was published on February 12, 2020 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2019-19921 — runc

HIGHFix: opencontainers/runc#2190

CVE-2019-19921 is a high-severity (CVSS 7) CWE-706 vulnerability in github.com/opencontainers/runc. A fix is available for github.com/opencontainers/runc — see the affected versions and patch details below.

opencontainers runc contains procfs race condition with a shared volume mount

Also known asGHSA-fh74-hm69-rqjwGO-2021-0087

Published

Feb 12, 2020

Updated

Jul 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2019-19921 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐹github.com/opencontainers/runc

Real-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

Impact

By crafting a malicious root filesystem (with /proc being a symlink to a directory which was inside a volume shared with another running container), an attacker in control of both containers can trick runc into not correctly configuring the container's security labels and not correctly masking paths inside /proc which contain potentially-sensitive information about the host (or even allow for direct attacks against the host).

In order to exploit this bug, an untrusted user must be able to spawn custom containers with custom mount configurations (such that a volume is shared between two containers). It should be noted that we consider this to be a fairly high level of access for an untrusted user -- and we do not recommend allowing completely untrusted users to have such degrees of access without further restrictions.

Specific Go Package Affected

github.com/opencontainers/runc/libcontainer

Patches

This vulnerability has been fixed in 1.0.0-rc10. It should be noted that the current fix is effectively a hot-fix, and there are known ways for it to be worked around (such as making the entire root filesystem a shared volume controlled by another container). We recommend that users review their access policies to ensure that untrusted users do not have such high levels of controls over container mount configuration.

Workarounds

If you are not providing the ability for untrusted users to configure mountpoints for runc (or through a higher-level tool such as docker run -v) then you are not vulnerable to this issue. This exploit requires fairly complicated levels of access (which are available for some public clouds but are not necessarily available for all deployments).

Additionally, it appears as though it is not possible to exploit this vulnerability through Docker (due to the order of mounts Docker generates). However you should not depend on this, as it may be possible to work around this roadblock.

Credits

This vulnerability was discovered by Cure53, as part of a third-party security audit.

For more information

If you have any questions or comments about this advisory:

Open an issue.
Email us at [email protected], or [email protected] if you think you've found a security bug.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/opencontainers/runc`	all versions	1.0.0-rc9.0.20200122160610-2fc03cc11c77`go get github.com/opencontainers/runc@v1.0.0-rc9.0.20200122160610-2fc03cc11c77`

Affected Products

5 products · 17 configurations

ubuntu linuxcanonical

2 versions

18.0419.10

debian linuxdebian

2 versions

9.010.0

Application

runclinuxfoundation

≤ 0.1.1

1 version

1.0.0

leapopensuse

1 version

15.1

Application

openshift container platformredhat

2 versions

4.14.2

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/opencontainers/runc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/opencontainers/runc to 1.0.0-rc9.0.20200122160610-2fc03cc11c77 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-19921 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.

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 HatModerate

For Red Hat OpenStack Platform, because runc is not directly used by the director-operator, no update will be provided at this time for the operator containers.

Product	Fixed in	Advisory
Red Hat Enterprise Linux 7 Extras	`runc-0:1.0.0-66.rc8.el7_7`	RHSA-2020:0942
Red Hat Enterprise Linux 8	`container-tools:rhel8-8020020200324071414.0d58ad57`	RHSA-2020:1650
Red Hat OpenShift Container Platform 4.1	`runc-0:1.0.0-63.rc8.rhaos4.1.git3cbe540.el8_0`	RHSA-2020:0695
Red Hat OpenShift Container Platform 4.2	`runc-0:1.0.0-63.rc10.rhaos4.2.gitdc9208a.el8`	RHSA-2020:0688
Red Hat OpenShift Container Platform 4.3	`runc-0:1.0.0-66.rc10.rhaos4.3.el7_8`	RHSA-2020:1485

UbuntuHIGH

USN-4297-1Ubuntu USN-6088-2Ubuntu

Frequently Asked Questions

### Impact By crafting a malicious root filesystem (with `/proc` being a symlink to a directory which was inside a volume shared with another running container), an attacker in control of both containers can trick `runc` into not correctly configuring the container's security labels and not correctly masking paths inside `/proc` which contain potentially-sensitive information about the host (or even allow for direct attacks against the host). In order to exploit this bug, an untrusted user must be able to spawn custom containers with custom mount configurations (such that a volume is shared b

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