CVE-2026-41579: runc Vulnerability Allowing Host Filesystem Integrity Violations via Malicious Symlinks
Summary
CVE-2026-41579: runc: Malicious image with /dev symlink can trigger limited host filesystem integrity violations. Affects github.com/opencontainers/runc across 3 version ranges.
< 1.3.6
>= 1.4.0, < 1.4.3
>= 1.5.0-rc.1, < 1.5.0-rc.3
Fixed in 1.3.6, 1.4.3 or 1.5.0-rc.3, depending on the release line you run. How to fix ↓
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Background
runc is a lightweight container runtime that is widely used for managing containerized applications. It is designed to create and manage containers according to the Open Container Initiative (OCI) specifications. runc is integral to various container orchestration platforms, providing a standardized interface for running containers. However, it has been found to be vulnerable to a specific issue where malicious container images can exploit symlinks to affect the host filesystem integrity.
Vulnerability Detail
The vulnerability arises during the setup of the container root filesystem, specifically in the functions setupPtmx and setupDevSymlinks. These functions utilize os.Remove and os.Symlink with a filepath.Join string, which can be manipulated by an image containing a symlink from /dev. This can lead to the deletion of files named ptmx on the host or the creation of arbitrary symlinks in pre-existing directories on the host. While the impact is limited due to certain mitigating factors, it poses a risk for users of container runtimes like Podman and containerd that do not mask malicious symlinks as Docker does.
How To Fix
Latest published version: v1.5.2 as of 22 Oct 2026
go get github.com/opencontainers/runc@v1.5.2Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 1.3.61.3.6go get github.com/opencontainers/runc@v1.3.6 -
>= 1.4.0, < 1.4.31.4.3go get github.com/opencontainers/runc@v1.4.3 -
>= 1.5.0-rc.1, < 1.5.0-rc.31.5.0-rc.3go get github.com/opencontainers/runc@v1.5.0-rc.3
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
Using user namespaces can significantly restrict the attack surface, limiting the attacker's ability to create or delete inodes to directories where the remapped root user has write access. Additionally, implementing Linux Security Modules (LSMs) like SELinux or AppArmor can help restrict the filesystem operations that runc can perform.
Conclusion
The runc vulnerability CVE-2026-41579 poses a moderate risk to users of certain container runtimes. It is crucial to update to the latest patched versions to mitigate potential impacts. Users should also consider implementing workarounds to further secure their systems against this vulnerability.
See every vulnerability recorded for github.com/opencontainers/runc →
FAQ
The vulnerability allows malicious container images to exploit symlinks, potentially leading to host filesystem integrity violations.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which monitors open-source vulnerabilities in real-time.
The primary impacts include the deletion of files named ptmx on the host and the creation of arbitrary symlinks, which could lead to configuration errors or denial of service in some cases.
No, this vulnerability is not exploitable in Docker due to its implementation of a top-level read-only layer that masks malicious symlinks.
If immediate updates are not possible, consider using user namespaces and LSMs to mitigate the risk until you can apply the patch.
References
Related vulnerabilities
Recent vulnerabilities recorded for github.com/opencontainers/runc.
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