# CVE-2026-39890: PraisonAI Affected by Remote Code Execution via YAML Deserialization in Agent Definition Loading

> Attackers can achieve remote code execution by uploading malicious YAML agent definitions due to unsafe deserialization in PraisonAI.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Apr 2026
- **Updated:** 9 Apr 2026
- **Also known as:** GHSA-32vr-5gcf-3pw2, PYSEC-2026-462

## What is CVE-2026-39890?

CVE-2026-39890 is a critical unsafe deserialization vulnerability in MervinPraison PraisonAI, published on 8 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

PraisonAI is a multi-agent teams system. Prior to 4.5.115, the AgentService.loadAgentFromFile method uses the js-yaml library to parse YAML files without disabling dangerous tags (such as !!js/function and !!js/undefined). This allows an attacker to craft a malicious YAML file that, when parsed, executes arbitrary JavaScript code. An attacker can exploit this vulnerability by uploading a malicious agent definition file via the API endpoint, leading to remote code execution (RCE) on the server. This vulnerability is fixed in 4.5.115.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-39890?

3 open source packages ship an affected version, including praisonai. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `praisonai` | PyPI | All versions | 4.5.115 |
| `praisonai` | PyPI | All versions | 4.5.115 |
| `praisonai` | PyPI | All versions | 4.5.115 |

Products: Praison Praisonai.

## How do I fix CVE-2026-39890?

Upgrade praisonai to 4.5.115 or later.

## Is CVE-2026-39890 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39890 exists.

## Other vulnerabilities in MervinPraison PraisonAI

- [CVE-2026-39888](https://insights.sbomify.com/CVE-2026-39888/): PraisonAIAgents has a sandbox escape via exception frame traversal in `execute_code` (subprocess mode) (critical 10.0)
- [CVE-2026-41497](https://insights.sbomify.com/CVE-2026-41497/): Incomplete fix for CVE-2026-34935: Command Injection in MervinPraison/PraisonAI (critical 9.8)
- [CVE-2026-40288](https://insights.sbomify.com/CVE-2026-40288/): PraisonAI: Critical RCE via `type: job` workflow YAML (critical 9.8)
- [CVE-2026-34934](https://insights.sbomify.com/CVE-2026-34934/): PraisonAI: Second-Order SQL Injection in `get_all_user_threads` (critical 9.8)
- [CVE-2026-34935](https://insights.sbomify.com/CVE-2026-34935/): PraisonAI: OS Command Injection in MCPHandler.parse_mcp_command() (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39890 and fix it if it is affected.

What it is: CVE-2026-39890 is a critical unsafe deserialization vulnerability in MervinPraison PraisonAI, published on 8 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39890 exists.

Affected packages and fixed versions:
- praisonai (PyPI): affected all versions; fixed in 4.5.115
- praisonai (PyPI): affected all versions; fixed in 4.5.115
- praisonai (PyPI): affected all versions; fixed in 4.5.115

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-2026-39890/ (Markdown: https://insights.sbomify.com/CVE-2026-39890/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39890
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39890
- OSV: https://osv.dev/vulnerability/CVE-2026-39890

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39890/
Summaries are generated and may contain mistakes; the official description above is the record.