CVE-2026-40112 PraisonAI has Stored XSS via Unsanitized Agent Output in HTML Rendering (nh3 Not a Required Dependency)
Attackers can inject arbitrary JavaScript into PraisonAI agent outputs, leading to stored XSS in browsers viewing the API.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-40112?
CVE-2026-40112 is a medium-severity cross-site scripting vulnerability in MervinPraison PraisonAI, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
PraisonAI is a multi-agent teams system. Prior to 4.5.128, the Flask API endpoint in src/praisonai/api.py renders agent output as HTML without effective sanitization. The _sanitize_html function relies on the nh3 library, which is not listed as a required or optional dependency in pyproject.toml. When nh3 is absent (the default installation), the sanitizer is a no-op that returns HTML unchanged. An attacker who can influence agent input (via RAG data poisoning, web scraping results, or prompt injection) can inject arbitrary JavaScript that executes in the browser of anyone viewing the API output. This vulnerability is fixed in 4.5.128.
Weakness: CWE-79
Which versions are affected by CVE-2026-40112?
3 open source packages ship an affected version, including praisonai and PraisonAI. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
praisonai PyPI | All versions | 4.5.128 |
praisonai PyPI | All versions | 4.5.128 |
PraisonAI PyPI | All versions | 4.5.128 |
Products include Praison Praisonai.
How do I fix CVE-2026-40112?
Upgrade praisonai to 4.5.128 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-40112 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40112 exists.
Other vulnerabilities in MervinPraison PraisonAI
- CVE-2026-39888 PraisonAIAgents has a sandbox escape via exception frame traversal in `execute_code` (subprocess mode)
- CVE-2026-41497 Incomplete fix for CVE-2026-34935: Command Injection in MervinPraison/PraisonAI
- CVE-2026-40288 PraisonAI: Critical RCE via `type: job` workflow YAML
- CVE-2026-39890 PraisonAI Affected by Remote Code Execution via YAML Deserialization in Agent Definition Loading
- CVE-2026-34934 PraisonAI: Second-Order SQL Injection in `get_all_user_threads`
Sources
Also known as GHSA-cfg2-mxfj-j6pw, PYSEC-2026-2910.