How severe is CVE-2025-43866?

No CVSS score has been assigned to CVE-2025-43866 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-43866?

CVE-2025-43866 affects the following packages: vantage6-server (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-43866?

Update vantage6-server to 4.11.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-43866 is resolved across your whole dependency graph.

How do I detect CVE-2025-43866 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vantage6-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-43866 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2025-43866 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-43866 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-43866?

CVE-2025-43866 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-43866?

CVE-2025-43866 is classified as Insufficient Random Values (CWE-330). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-43866 published, and has it been updated?

CVE-2025-43866 was published on June 12, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2025-43866 — vantage6-server

Fix: vantage6/vantage6@e39a262

CVE-2025-43866 is a Insufficient Random Values vulnerability in vantage6-server. A fix is available for vantage6-server — see the affected versions and patch details below.

Vantage6 Server JWT secret not cryptographically secure

Also known asGHSA-m3mq-f375-5vghPYSEC-2025-221

Published

Jun 12, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-43866.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍vantage6-server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The JWT secret key in the vantage6 server is auto-generated unless defined by the user. The auto-generated key is a UUID1, which is not cryptographically secure as it is predictable to some extent

Patches

Workarounds

You may define JWT secret key in the server configuration file

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`vantage6-server`	all versions	4.11.0`pip install --upgrade 'vantage6-server==4.11.0'`

Affected Products

1 product · 1 configurations

Application

vantage6vantage6

< 4.11.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vantage6-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vantage6-server to 4.11.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-43866 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact The JWT secret key in the vantage6 server is auto-generated unless defined by the user. The auto-generated key is a UUID1, which is not cryptographically secure as it is [predictable to some extent](https://docs.python.org/3/library/uuid.html#uuid.uuid1) ### Patches No ### Workarounds You may define JWT secret key in the server configuration file

O3 Security · Impact-Aware SCA

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