CVE-2021-21249
Post-Auth Unsafe Yaml deserialization
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
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Post-Auth Unsafe Yaml deserialization
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
- Record
CVE-2021-21249- CVSS 3.1
- 9.6 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-74
- Updated
- 2026-11-02
EUVDEUVD-2021-8632
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
- Record
EUVD-2021-8632- CVSS 3.1
- 9.6 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N - Updated
- 2026-11-03
NVD
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
- Record
CVE-2021-21249- CVSS 3.1
- 9.6 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 6.5 Medium
AV:N/AC:L/Au:S/C:P/I:P/A:P - Weakness
- CWE-74, CWE-502
- Updated
- 2026-11-02
OSV
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
- Record
CVE-2021-21249- CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-21249 is a critical vulnerability (CVSS 9.6) in Onedev Project Onedev, published January 15, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.06%, the 87th percentile. No source names a fixed version.