CVE-2021-21249

What it is

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

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

3.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-01-15 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:35 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.1% in the next 30 days (EPSS).
• Severity: 9.6 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-01-15 21:15 UTC

Last modified

2026-06-17 03:35 UTC

Exploit probability

3.1% · EPSS, next 30 days

Weakness

CWE-74

Record status

Modified

Affected

• Onedev Project Onedev < 4.0.3

Attack profile CVSS 3.1 · 9.6

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-21249.md and follow it. Check whether this project is affected by CVE-2021-21249. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge