CVE-2026-50203 Overview
CVE-2026-50203 is a path traversal vulnerability in the Apache Airflow SFTP provider package (apache-airflow-providers-sftp). The flaw resides in SFTPHook.retrieve_directory and SFTPOperator(operation=get), which fail to validate directory-entry names returned by a remote SFTP server. A malicious or compromised SFTP server can return crafted file names containing traversal sequences, causing Airflow workers to write files outside the configured local destination directory. Exploitation requires no Airflow account, since the attack surface is any deployment that downloads directories from an untrusted SFTP server. The issue is tracked under [CWE-22] and is fixed in apache-airflow-providers-sftp version 5.8.1.
Critical Impact
A compromised remote SFTP server can write arbitrary files to attacker-chosen paths on Airflow workers, enabling code execution through overwrite of DAGs, configuration files, or SSH keys.
Affected Products
- Apache Airflow SFTP provider (apache-airflow-providers-sftp) versions prior to 5.8.1
- Apache Airflow deployments using SFTPHook.retrieve_directory
- Apache Airflow deployments using SFTPOperator with operation=get
Discovery Timeline
- 2026-06-17 - CVE-2026-50203 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-50203
Vulnerability Analysis
The Apache Airflow SFTP provider exposes two interfaces for retrieving directories from remote SFTP servers: SFTPHook.retrieve_directory and SFTPOperator invoked with operation=get. Both interfaces iterate over directory entries returned by the remote server and construct local destination paths by joining the configured local directory with the entry name supplied by the server.
The implementation trusts entry names provided by the remote server. When an entry name contains path traversal sequences such as ../ or an absolute path, the resulting destination path escapes the configured local directory. Airflow workers then write attacker-controlled file contents to attacker-chosen locations on the host filesystem.
Root Cause
The root cause is missing validation and canonicalization of remote filenames before path concatenation. The provider does not enforce that the resolved destination path remains within the configured download directory. This is a classic CWE-22 path traversal pattern triggered through a server-to-client trust boundary rather than user input.
Attack Vector
The attack vector is network-based and requires no authentication on the Airflow side. An attacker who controls or compromises an SFTP server that an Airflow DAG connects to can serve directory listings containing crafted entry names. When the worker downloads the directory, files land outside the intended destination. Targets include Airflow DAG directories, Python site-packages, SSH authorized_keys files, and configuration files, any of which can lead to code execution under the Airflow worker identity.
No proof-of-concept code is publicly available. See the Apache Mailing List Thread and the GitHub Pull Request for Airflow for technical details of the fix.
Detection Methods for CVE-2026-50203
Indicators of Compromise
- Files created outside configured SFTP download directories on Airflow worker hosts following directory retrieval tasks.
- Unexpected modifications to Airflow DAG directories, Python package directories, or ~/.ssh/authorized_keys on worker hosts.
- Airflow task logs showing SFTPHook.retrieve_directory or SFTPOperator get operations referencing files with .. or absolute path components.
Detection Strategies
- Inventory all DAGs using SFTPOperator with operation=get or calling SFTPHook.retrieve_directory, and cross-reference against the installed provider version.
- Audit Airflow worker filesystems for files written outside declared SFTP destination paths after directory download tasks.
- Enable verbose SFTP transfer logging and alert on filenames containing .., leading /, or non-printable characters returned by remote servers.
Monitoring Recommendations
- Monitor file integrity on Airflow DAG folders, plugin directories, and the worker user's home directory.
- Alert on outbound SFTP connections from Airflow workers to untrusted or newly observed remote hosts.
- Track installed versions of apache-airflow-providers-sftp across all Airflow schedulers and workers, flagging any release below 5.8.1.
How to Mitigate CVE-2026-50203
Immediate Actions Required
- Upgrade apache-airflow-providers-sftp to version 5.8.1 or later on all Airflow components.
- Inventory DAGs that download directories from external SFTP servers and pause those using untrusted remote hosts until patched.
- Review Airflow worker filesystems for unexpected files written since the SFTP provider was first deployed.
Patch Information
The Apache Airflow project addressed the vulnerability in apache-airflow-providers-sftp 5.8.1. The fix validates that each resolved destination path remains within the configured local download directory before writing. Refer to the GitHub Pull Request for Airflow and the Apache Mailing List Thread for the upstream change.
Workarounds
- Restrict SFTP connections in DAGs to trusted, organization-controlled servers until the provider is upgraded.
- Run Airflow workers under a least-privilege account with no write access to DAG folders, Python site-packages, or SSH key files.
- Replace directory download operations with single-file get calls where filenames are explicitly enumerated by the DAG.
# Upgrade the SFTP provider on every Airflow scheduler and worker
pip install --upgrade 'apache-airflow-providers-sftp>=5.8.1'
# Verify the installed version
pip show apache-airflow-providers-sftp | grep -i version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
