runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7 and below, 1.3.0-rc.1 through 1.3.1, 1.4.0-rc.1 and 1.4.0-rc.2 files, runc would not perform sufficient verification that the source of the bind-mount (i.e., the container's /dev/null) was actually a real /dev/null inode when using the container's /dev/null to mask. This exposes two methods of attack: an arbitrary mount gadget, leading to host information disclosure, host denial of service, container escape, or a bypassing of maskedPaths. This issue is fixed in versions 1.2.8, 1.3.3 and 1.4.0-rc.3.
History

Thu, 06 Nov 2025 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Opencontainers
Opencontainers runc
Vendors & Products Opencontainers
Opencontainers runc

Thu, 06 Nov 2025 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 06 Nov 2025 19:00:00 +0000

Type Values Removed Values Added
Description A flaw was found in runc. This flaw exploits an issue with how masked paths are implementedin runc. When masking files, runc will bind-mount the container's /dev/null inode on top of the file. However, if an attacker can replace /dev/null with a symlink to some other procfs file, runc will instead bind-mount the symlink target read-write. runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7 and below, 1.3.0-rc.1 through 1.3.1, 1.4.0-rc.1 and 1.4.0-rc.2 files, runc would not perform sufficient verification that the source of the bind-mount (i.e., the container's /dev/null) was actually a real /dev/null inode when using the container's /dev/null to mask. This exposes two methods of attack: an arbitrary mount gadget, leading to host information disclosure, host denial of service, container escape, or a bypassing of maskedPaths. This issue is fixed in versions 1.2.8, 1.3.3 and 1.4.0-rc.3.
Title runc: container escape via 'masked path' abuse due to mount race conditions runc container escape via "masked path" abuse due to mount race conditions
Weaknesses CWE-363
CWE-61
References
Metrics cvssV4_0

{'score': 7.3, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H'}


Thu, 06 Nov 2025 12:15:00 +0000

Type Values Removed Values Added
Description A flaw was found in runc. This flaw exploits an issue with how masked paths are implementedin runc. When masking files, runc will bind-mount the container's /dev/null inode on top of the file. However, if an attacker can replace /dev/null with a symlink to some other procfs file, runc will instead bind-mount the symlink target read-write.
Title runc: container escape via 'masked path' abuse due to mount race conditions
Weaknesses CWE-59
References
Metrics threat_severity

None

cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H'}

threat_severity

Important


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2025-11-06T18:47:47.335Z

Updated: 2025-11-06T19:22:22.047Z

Reserved: 2025-03-26T15:04:52.627Z

Link: CVE-2025-31133

cve-icon Vulnrichment

Updated: 2025-11-06T19:08:17.594Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-11-06T19:15:41.343

Modified: 2025-11-06T19:45:09.883

Link: CVE-2025-31133

cve-icon Redhat

Severity : Important

Publid Date: 2025-11-05T00:00:00Z

Links: CVE-2025-31133 - Bugzilla