What is CVE-2026-34939?

CVE-2026-34939 is a medium-severity vulnerability in Mervinpraison Praisonai, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2026-04-03.

How severe is CVE-2026-34939?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mervinpraison Praisonai

CVE-2026-34939

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.

Vulnerability class: ReDoS (Regular Expression Denial of Service)

EPSS: 0.004 (32.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Affected products

Mervinpraison Praisonai — versions < 4.5.90
Praison Praisonai

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2026-34939?: CVE-2026-34939 is a medium-severity vulnerability in Mervinpraison Praisonai, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2026-04-03.
How severe is CVE-2026-34939?: Medium severity. CVSS v3 base score is 6.5 out of 10.