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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-34939?
3 open source packages ship an affected version, including praisonai. It affects 1 product.
| Package | 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 include Praison Praisonai.
How do I fix CVE-2026-34939?
Upgrade praisonai to 4.5.90 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
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 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-8w9j-hc3g-3g7f, PYSEC-2026-2907.