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

> Attackers can cause service outages in PraisonAI by supplying malicious regex patterns that trigger catastrophic backtracking, requiring an upgrade to fix.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Apr 2026
- **Updated:** 6 Apr 2026
- **Also known as:** GHSA-8w9j-hc3g-3g7f, PYSEC-2026-2907

## What is CVE-2026-34939?

CVE-2026-34939 is a medium-severity denial of service vulnerability in MervinPraison PraisonAI, published on 3 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-34939?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `praisonai` | PyPI | All versions | 4.5.90 |
| `praisonai` | PyPI | All versions | 4.5.90 |
| `praisonai` | PyPI | All versions | 4.5.90 |

Products: Praison Praisonai.

## How do I fix CVE-2026-34939?

Upgrade praisonai to 4.5.90 or later.

## Is CVE-2026-34939 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34939 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-2026-39890](https://insights.sbomify.com/CVE-2026-39890/): PraisonAI Affected by Remote Code Execution via YAML Deserialization in Agent Definition Loading (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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34939 and fix it if it is affected.

What it is: CVE-2026-34939 is a medium-severity denial of service vulnerability in MervinPraison PraisonAI, published on 3 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34939 exists.

Affected packages and fixed versions:
- praisonai (PyPI): affected all versions; fixed in 4.5.90
- praisonai (PyPI): affected all versions; fixed in 4.5.90
- praisonai (PyPI): affected all versions; fixed in 4.5.90

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-2026-34939/ (Markdown: https://insights.sbomify.com/CVE-2026-34939/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34939
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34939
- OSV: https://osv.dev/vulnerability/CVE-2026-34939

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34939/
Summaries are generated and may contain mistakes; the official description above is the record.