# CVE-2021-21247: Post-Auth Unsafe Deserialization on BasePage (AJAX)

> Authenticated attackers can achieve remote code execution via unsafe deserialization of AJAX parameters in OneDev.

- **Severity:** Critical 9.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Jan 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-6pxf-75cf-vwjp

## What is CVE-2021-21247?

CVE-2021-21247 is a critical unsafe deserialization vulnerability in theonedev onedev, published on 15 Jan 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, the application's BasePage registers an AJAX event listener (`AbstractPostAjaxBehavior`) in all pages other than the login page. This listener decodes and deserializes the `data` query parameter. We can access this listener by submitting a POST request to any page. This issue may lead to `post-auth RCE` This endpoint is subject to authentication and, therefore, requires a valid user to carry on the attack. This issue was addressed in 4.0.3 by encrypting serialization payload with secrets only known to server.

Weakness: CWE-502 (Deserialization of Untrusted Data), CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2021-21247?

It affects 1 product.


Products: Onedev Project Onedev.

## How do I fix CVE-2021-21247?

No fix has been published for CVE-2021-21247 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21247 being exploited?

There is no known exploitation of CVE-2021-21247 in the wild and no public exploit code.

## Other vulnerabilities in theonedev onedev

- [CVE-2021-21242](https://insights.sbomify.com/CVE-2021-21242/): Pre-Auth Unsafe Deserialization on AttachmentUploadServet (critical 10.0)
- [CVE-2021-21243](https://insights.sbomify.com/CVE-2021-21243/): Pre-Auth Unsafe Deserialization on KubernetesResource (critical 10.0)
- [CVE-2021-21244](https://insights.sbomify.com/CVE-2021-21244/): Pre-Auth SSTI via Bean validation message tampering (critical 10.0)
- [CVE-2021-21245](https://insights.sbomify.com/CVE-2021-21245/): Pre-Auth Arbitrary File Upload (critical 10.0)
- [CVE-2022-39206](https://insights.sbomify.com/CVE-2022-39206/): CI/CD Docker Escape in OneDev (critical 9.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21247 and fix it if it is affected.

What it is: CVE-2021-21247 is a critical unsafe deserialization vulnerability in theonedev onedev, published on 15 Jan 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-21247 in the wild and no public exploit code.

Affected product: theonedev onedev. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-21247/ (Markdown: https://insights.sbomify.com/CVE-2021-21247/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21247
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21247
- OSV: https://osv.dev/vulnerability/CVE-2021-21247

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21247/
Summaries are generated and may contain mistakes; the official description above is the record.