Deserialization in Mervinpraison Praisonai

CVE-2026-39890

PraisonAI is a multi-agent teams system. Prior to 4.5.115, the AgentService.loadAgentFromFile method uses the js-yaml library to parse YAML files without disabling dangerous tags (such as !!js/function and !!js/undefined). This allows an attacker to craft a malicious YAML file that, when parsed, executes arbitrary JavaScript code. An attacker can exploit this vulnerability by uploading a malicious agent definition file via the API endpoint, leading to remote code execution (RCE) on the server. This vulnerability is fixed in 4.5.115.

Vulnerability class: Insecure Deserialization

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (55.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 55.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-39890: held from 0.006 to 0.008.

EPSS over last 30 days · oldest: 0.006 · newest: 0.008 · change: +0.002

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-39890?
CVE-2026-39890 is a critical-severity vulnerability in Mervinpraison Praisonai, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-04-08.
How severe is CVE-2026-39890?
Critical severity. CVSS v3 base score is 9.8 out of 10.