Description

Buildah is a tool that facilitates building OCI images. From 1.38.1 until 1.43.2 and 1.44.0, TempDirForURL in define/types.go does not securely confine Git repository subdirectories to the downloaded build context, and downloadToDirectory and stdinToDirectory can follow a Dockerfile symlink left by a partially extracted tar archive. A malicious server supplying a Git repository or tar archive can cause files outside the build context directory to be included in the context or copied into the build. This issue is fixed in versions 1.43.2 and 1.44.0.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.3",
  "pubDate": "2026-08-21T21:16:59.250Z",
  "pubdate": "2026-08-21T21:16:59.250Z",
  "executiveSummary": "A path traversal and symlink-following vulnerability exists in Buildah within the TempDirForURL function in define/types.go, as well as the downloadToDirectory and stdinToDirectory routines. This security flaw allows a malicious server supplying a Git repository or a partially extracted tar archive to bypass intended build context boundaries. Consequently, an attacker can cause files located outside the designated build context directory to be improperly included within the context or copied directly into the resulting OCI image build. The vulnerability affects Buildah versions from 1.38.1 until 1.43.2 and version 1.44.0. The potential impact involves unauthorized disclosure, inclusion, or modification of sensitive host or system files during the container image construction process. Attackers require the capability to control or spoof a remote Git repository or supply a malicious tar archive consumed by the build process. Successful exploitation relies on tricking the build system into processing untrusted remote content or malicious archives without requiring prior authentication or elevated privileges within the build environment, presenting significant supply chain security risks.",
  "technicalDetails": "The root cause of the vulnerability stems from insufficient validation and sanitization within define/types.go via TempDirForURL, alongside insecure file handling mechanisms implemented in downloadToDirectory and stdinToDirectory. Specifically, TempDirForURL fails to securely confine Git repository subdirectories to the boundaries of the downloaded build context. Concurrently, downloadToDirectory and stdinToDirectory fail to adequately protect against symbolic links, allowing them to follow Dockerfile symlinks strategically placed inside a partially extracted tar archive. The vulnerable components are specific functions responsible for handling remote context acquisition and archive extraction within the Buildah codebase. Affected versions include Buildah from 1.38.1 up to, but excluding, 1.43.2, and version 1.44.0. Exploitation does not require authentication or specific privilege levels on the target system executing Buildah, but it assumes network exposure or direct interaction with an untrusted remote Git server or malicious archive source. The attack flow initiates when a user executes a build command referencing a malicious remote Git repository or extracts an untrusted tar archive. During the Git repository handling phase, the inadequate confinement enforced by TempDirForURL enables directory traversal conditions. When processing a malicious tar archive, the extraction logic evaluates and follows a Dockerfile symlink left by a partially extracted archive. This behavior permits the attacker to traverse outside the intended build context directory. Consequently, payload behavior includes reading, referencing, or copying arbitrary files residing outside the build context into the container image build context. The post-exploitation impact compromises the integrity and confidentiality of the build environment and the resulting OCI image, potentially leading to the inclusion of sensitive host files into container artifacts."
}