How severe is CVE-2026-4400?

CVE-2026-4400 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.

Is CVE-2026-4400 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-4400?

CVE-2026-4400 affects 1millionbot Millie Chatbot. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-4400?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-4400 have an EU (EUVD) identifier?

Yes. CVE-2026-4400 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17359.

When was CVE-2026-4400 published?

CVE-2026-4400 was published on 2026-03-31 and last updated on 2026-06-17.

CVE-2026-4400

CVE-2026-4400 is a medium-severity vulnerability in 1millionbot Millie Chatbot with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-639.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 7.0
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-17359
Weakness: CWE-639
Affected product: 1millionbot Millie Chatbot
Published: 2026-03-31
Last modified: 2026-06-17

Description

Insecure Direct Object Reference (IDOR) vulnerability in 1millionbot Millie chat that allows private conversations of other users being viewed by simply changing the conversation ID. The vulnerability is present in the endpoint 'api.1millionbot.com/api/public/conversations/' and, if exploited, could allow a remote attacker to access other users private chatbot conversations, revealing sensitive or confidential data without requiring credentials or impersonating users. In order for the vulnerability to be exploited, the attacker must have the user's conversation ID.

Frequently asked questions

What is CVE-2026-4400?: Insecure Direct Object Reference (IDOR) vulnerability in 1millionbot Millie chat that allows private conversations of other users being viewed by simply changing the conversation ID. The vulnerability is present in the endpoint 'api.1millionbot.com/api/public/conversations/' and, if exploited, could allow a remote attacker to access other users private chatbot conversations, revealing sensitive or confidential data without requiring credentials or impersonating users. In order for the vulnerability to be exploited, the attacker must have the user's conversation ID.
How severe is CVE-2026-4400?: CVE-2026-4400 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.
Is CVE-2026-4400 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-4400?: CVE-2026-4400 affects 1millionbot Millie Chatbot. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-4400?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-4400 have an EU (EUVD) identifier?: Yes. CVE-2026-4400 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17359.
When was CVE-2026-4400 published?: CVE-2026-4400 was published on 2026-03-31 and last updated on 2026-06-17.

References

https://www.incibe.es/en/incibe-cert/notices/aviso/multiple-vulnerabilities-1millionbot-millie-chatbot

Affected products (1)

cpe:2.3:a:1millionbot:millie_chatbot:*:*:*:*:*:*:*:*

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