BaseFortify

Publication date: 2025-11-06

Last updated on: 2025-12-03

Assigner: GitHub, Inc.

Description

runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7, 1.3.2 and 1.4.0-rc.2, an attacker can trick runc into misdirecting writes to /proc to other procfs files through the use of a racing container with shared mounts (we have also verified this attack is possible to exploit using a standard Dockerfile with docker buildx build as that also permits triggering parallel execution of containers with custom shared mounts configured). This redirect could be through symbolic links in a tmpfs or theoretically other methods such as regular bind-mounts. While similar, the mitigation applied for the related CVE, CVE-2019-19921, was fairly limited and effectively only caused runc to verify that when LSM labels are written they are actually procfs files. This issue is fixed in versions 1.2.8, 1.3.3, and 1.4.0-rc.3.

CVSS Scores

EPSS Scores

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Meta Information

Published

2025-11-06

Last Modified

2025-12-03

Generated

2026-07-06

AI Q&A

2025-11-06

EPSS Evaluated

2026-07-05

NVD

CVE-2025-52881

Affected Vendors & Products

Vendor	Product	Version / Range
linuxfoundation	runc	to 1.2.8 (exc)
linuxfoundation	runc	From 1.3.0 (inc) to 1.3.3 (exc)
linuxfoundation	runc	1.4.0
linuxfoundation	runc	1.4.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-61	The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
CWE-363	The product checks the status of a file or directory before accessing it, which produces a race condition in which the file can be replaced with a link before the access is performed, causing the product to access the wrong file.

Attack-Flow Graph

Executive Summary

This vulnerability in runc allows an attacker to trick runc into misdirecting writes to /proc to other procfs files by exploiting a race condition with containers that share mounts. This can be done using symbolic links in tmpfs or other methods like bind-mounts. The issue affects certain versions of runc and is fixed in later versions.

Impact Analysis

The vulnerability can allow an attacker to redirect writes intended for /proc to other procfs files, potentially leading to unauthorized modification of system files or data within containers. This could compromise container isolation and security, leading to privilege escalation or data integrity issues.

Mitigation Strategies

Upgrade runc to version 1.2.8, 1.3.3, or 1.4.0-rc.3 or later, as these versions contain the fix for this vulnerability.

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