Security Digest · Vulnerability record
CVE-2026-39890: PraisonAI Vulnerable to Remote Code Execution via YAML Deserialization in Agent Definition Loading
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).
CVSS 9.8 Critical EPSS 0.8% · p56
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.8%, percentile 56: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 56% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
praisonai(PyPI) <= 4.5.114, fixed in 4.5.115. Check your lockfile, including transitive dependencies.
What it is
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.
From the GitHub advisory
Summary 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.
Details The vulnerability exists in the YAML deserialization process. The js-yaml library's load function is used without specifying a safe schema (e.g., JSONSCHEMA or DEFAULTSAFESCHEMA). This enables the parsing of JavaScript functions and other dangerous types. When a malicious YAML file containing a !!js/function tag is parsed, the function is evaluated, leading to arbitrary code execution.
The vulnerable code is located in src/agents/agent.service.ts at line 55.
PoC An attacker can create a malicious agent YAML file with the following content:
Then, upload this file as an agent definition via the API endpoint that uses AgentService.loadAgentFromFile. When the agent is loaded (either during startup or via an API call that triggers loading), the payload will execute the command touch /tmp/pwned, demonstrating arbitrary code execution.
Weakness type: CWE-502.
Product: praisonai (PyPI) · Assigned by: GitHub_M · Published: 2026-04-08
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | praisonai | <= 4.5.114 | 4.5.115 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| MervinPraison | PraisonAI | < 4.5.115 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.81% probability of exploitation activity in the next 30 days; percentile 56.
Timeline
- — CVE record published by GitHub_M
- — GitHub-reviewed advisory GHSA-32vr-5gcf-3pw2 published (critical)
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-32vr-5gcf-3pw2 github.com
- CVE.org record CVE-2026-39890 cve.org
- NVD entry CVE-2026-39890 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com