How severe is CVE-2021-3840?

CVE-2021-3840 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-3840?

CVE-2021-3840 affects the following packages: antilles-tools (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2021-3840?

Update antilles-tools to 1.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3840 is resolved across your whole dependency graph.

How do I detect CVE-2021-3840 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for antilles-tools. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-3840 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.

How does O3 Security protect against CVE-2021-3840?

O3 pinpoints whether CVE-2021-3840 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-3840 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-3840 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-2021-3840?

CVE-2021-3840 has an EPSS (Exploit Prediction Scoring System) score of 2.0%, placing it in the 78th 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.

When was CVE-2021-3840 published, and has it been updated?

CVE-2021-3840 was published on November 12, 2021 and was last updated on March 13, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2021-3840: Antilles Dependency Confusion Vulnerability (Hig…

EPSS Exploitation Probability

via FIRST.org ↗

2.0%probability of exploitation in next 30 days

Lower Risk78th percentile+0.79%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐍antilles-tools

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

A dependency confusion vulnerability was reported in the Antilles open-source software prior to version 1.0.1 that could allow for remote code execution during installation due to a package listed in requirements.txt not existing in the public package index (PyPi). MITRE classifies this weakness as an Uncontrolled Search Path Element (CWE-427) in which a private package dependency may be replaced by an unauthorized package of the same name published to a well-known public repository such as PyPi. The configuration has been updated to only install components built by Antilles, removing all other public package indexes. Additionally, the antilles-tools dependency has been published to PyPi.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`antilles-tools`	all versions	1.0.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for antilles-tools. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update antilles-tools to 1.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3840 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.
How O3 protects you
O3 pinpoints whether CVE-2021-3840 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2021-3840. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

A dependency confusion vulnerability was reported in the Antilles open-source software prior to version 1.0.1 that could allow for remote code execution during installation due to a package listed in requirements.txt not existing in the public package index (PyPi). MITRE classifies this weakness as an Uncontrolled Search Path Element (CWE-427) in which a private package dependency may be replaced by an unauthorized package of the same name published to a well-known public repository such as PyPi. The configuration has been updated to only install components built by Antilles, removing all othe

O3 Security · Impact-Aware SCA

Is CVE-2021-3840 in your dependencies?

O3 detects CVE-2021-3840 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2021-3840