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Servers and applications

CVE-2019-19921

procfs race condition with a shared volume mount

Severity
High 7.0
Published
28 Jan 2020
Last changed
17 Jun 2026
Added to UpHeron
1 Nov 2026
Fixed in
1.0.0-rc10
Exploit chance
0.4% in the next 30 daysHigher than 37% of CVEs. EPSS by FIRST, 10 Nov 2026
Also known as
GHSA-fh74-hm69-rqjw
Sources
NVD, Project advisories (GitHub)

Description

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.

From opencontainers/runc's security advisory.

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.

Workarounds as given by opencontainers/runc's security advisory.

Affected software

SoftwareAffected versions
runcServers and applications · cpe:a:linuxfoundation:runc
  • Version 1.0.0-rc9
  • Version 1.0.0-rc8
  • Version 1.0.0-rc7
  • Version 1.0.0-rc6
All 10 release lines
  • Every version up to 0.1.1
  • Version 1.0.0-rc1
  • Version 1.0.0-rc2
  • Version 1.0.0-rc3
  • Version 1.0.0-rc4
  • Version 1.0.0-rc5
  • Version 1.0.0-rc6
  • Version 1.0.0-rc7
  • Version 1.0.0-rc8
  • Version 1.0.0-rc9
runcServers and applications · github:opencontainers/runc
  • Every version before 1.0.0-rc10

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2019-19921
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2019-19921
  • GitHub Advisory Database https://github.com/advisories/GHSA-fh74-hm69-rqjw
  • github.com https://github.com/opencontainers/runc/security/advisories/GHSA-fh74-hm69-rqjw