8.2

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-28406

CVE-2026-28406: kaniko has tar archive path traversal in build context extraction allows writing files outside destination directory

kaniko is a tool to build container images from a Dockerfile, inside a container or Kubernetes cluster. Starting in version 1.25.4 and prior to version 1.25.10, kaniko unpacks build context archives using filepath.Join(dest, cleanedName) without enforcing that the final path stays within dest. A tar entry like ../outside.txt escapes the extraction root and writes files outside the destination directory. In environments with registry authentication, this can be chained with docker credential helpers to achieve code execution within the executor process. Version 1.25.10 uses securejoin for path resolution in tar extraction.

(GitHub Advisory)

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CVE-2026-28406

CVE-2026-28406:

8.2

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/chainguard-dev/kaniko	go	>= 1.25.4, < 1.25.10	1.25.10

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a classic path traversal issue within the tar archive extraction functionality of kaniko. The root cause is the usage of filepath.Join to construct file paths from tar headers without properly sanitizing the filenames. An attacker could craft a tar archive with entries containing ../ sequences (e.g., ../pwned.txt) to write files outside of the intended destination directory.

The analysis of the patch a370e4b1f66e6e842b685c8f70ed507964c4b221 clearly shows the vulnerable code and the corresponding fix. The primary vulnerable function is ExtractFile in pkg/util/fs_util.go, where the insecure path concatenation occurs. The UnTar function is the entry point that reads the malicious tar archive and passes the data to ExtractFile. Additionally, the GetFSFromLayers function had a similar flaw when processing whiteout files (.wh.), which could lead to arbitrary file deletion outside the target directory. The fix involves replacing the insecure filepath.Join with securejoin.SecureJoin and adding explicit checks to deny paths containing ../, thus confining all file operations to the intended directory.

Vulnerable functions

ExtractFile

pkg/util/fs_util.go

The function used `filepath.Join` to construct the destination path for a file from a tar archive without validating if the resulting path was within the destination directory. A malicious tar entry with `../` could cause file writes outside the `dest` directory.

UnTar

pkg/util/fs_util.go

This function processes a tar archive and calls the vulnerable `ExtractFile` function for each entry. By providing a malicious tar archive, an attacker can trigger the path traversal vulnerability in `ExtractFile`. The added test `TestUnTar_PathTraversal` confirms this is an entry point for the vulnerability.

GetFSFromLayers

pkg/util/fs_util.go

This function processes container image layers. When handling whiteout files (which indicate file deletions), it constructed a path using `filepath.Join` without proper sanitization. This could be exploited to delete files or directories outside the intended root directory via a path traversal attack in a malicious layer.

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Miggo AI

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WAF Rule

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Reasoning

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