CVE-2021-21249

OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, there is an issue involving YAML parsing which can lead to post-auth remote code execution. In order to parse and process YAML files, OneDev uses SnakeYaml which by default (when not using `SafeConstructor`) allows the instantiation of arbitrary classes. We can leverage that to run arbitrary code by instantiating classes such as `javax.script.ScriptEngineManager` and using `URLClassLoader` to load the script engine provider, resulting in the instantiation of a user controlled class. For a full example refer to the referenced GHSA. This issue was addressed in 4.0.3 by only allowing certain known classes to be deserialized

• CVE ID
• CVE-2021-21249

• Assigner
• security-advisories@github.com

• Vulnerability Status
• Analyzed

• Published Version
• 2021-01-15T21:15:13

• Last Modified Date
• 2022-04-26T16:13:44

• Version
• 2.0

• Vector String
• AV:N/AC:L/Au:S/C:P/I:P/A:P

• Access Vector
• NETWORK

• Access Compatibility
• LOW

• Authentication
• SINGLE

• Confidentiality Impact
• PARTIAL

• Integrity Impact
• PARTIAL

• Availability Impact
• PARTIAL

• Base Score
• 6.5

• Severity
• MEDIUM

• Exploitability Score
• 8

• Impact Score
• 6.4

• Version
• 3.1

• Vector String
• CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

• Attack Vector
• NETWORK

• Attack Compatibility
• LOW

• Privileges Required
• LOW

• User Interaction
• NONE

• Scope
• UNCHANGED

• Confidentiality Impact
• HIGH

• Availability Impact
• HIGH

• Base Score
• 8.8

• Base Severity
• HIGH

• Exploitability Score
• 2.8

• Impact Score
• 5.9