HOMEVULNERABILITIESCVE-2026-4399
HIGH

CVE-2026-4399

Published: March 31, 2026· Updated: Apr 1, 2026

8.7
CVSS v3.1
EPSS:0.22%probability of exploitation in 30 daysPercentile:45.0th

Official Description

Prompt injection vulnerability in 1millionbot Millie chatbot that occurs when a user manages to evade chat restrictions using Boolean prompt injection techniques (formulating a question in such a way that, upon receiving an affirmative response ('true'), the model executes the injected instruction), causing it to return prohibited information and information outside its intended context. Successful exploitation of this vulnerability could allow a malicious remote attacker to abuse the service for purposes other than those originally intended, or even execute out-of-context tasks using 1millionbot's resources and/or OpenAI's API key. This allows the attacker to evade the containment mechanisms implemented during LLM model training and obtain responses or chat behaviors that were originally restricted.

NVD Source

Technical Analysis

CVE-2026-4399 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeX
Impact
Confidentiality
Integrity
Availability
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
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All References (1)

Quick Facts

CVE IDCVE-2026-4399
CVSS Score8.7 / 10
SeverityHIGH
CISA KEVNo
EPSS (30d)0.22%
PublishedMar 31, 2026

Recommended Actions

  • Apply vendor patches immediately
  • Monitor CVE-2026-4399 in threat intel feeds
  • Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.