How severe is CVE-2021-40870?

CVE-2021-40870 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-40870?

Affected package information for CVE-2021-40870 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-40870?

No fixed release is recorded for CVE-2021-40870 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2021-40870 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2021-40870 if there is no patch (or I can't update yet)?

Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Is CVE-2021-40870 actively exploited in the wild?

Yes. There are 11 known exploit references for CVE-2021-40870, including 9 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-40870?

CVE-2021-40870 has an EPSS (Exploit Prediction Scoring System) score of 93.0%, placing it in the 100th 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-40870 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-40870 (Aviatrix Controller Unrestricted Upload of File) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-01-18. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-02-01. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-40870?

CVE-2021-40870 is classified as CWE-23 (CWE-23). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2021-40870?

A Nuclei detection template exists for CVE-2021-40870, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-40870 published, and has it been updated?

CVE-2021-40870 was published on September 13, 2021 and was last updated on October 21, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🛡️

CISA KEV · ACTIVELY EXPLOITED

CRITICAL severity

CVE-2021-40870

CRITICAL

CVE-2021-40870 is a critical-severity (CVSS 9.8) CWE-23 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-01-18) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

An issue was discovered in Aviatrix Controller 6.x before 6.5-1804.1922. Unrestricted upload of a file with a dangerous type is possible, which allows an unauthenticated user to execute…

Published

Sep 13, 2021

Updated

Oct 21, 2025

Affected

1 product

Patched

See advisory

Exploits

11 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-01-18. Federal agencies were required to remediate by 2022-02-01.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-40870.

EPSS Exploitation Probability

via FIRST.org ↗

93.0%probability of exploitation in next 30 days

Very High Risk0.00%

Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-40870 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

An issue was discovered in Aviatrix Controller 6.x before 6.5-1804.1922. Unrestricted upload of a file with a dangerous type is possible, which allows an unauthenticated user to execute arbitrary code via directory traversal.

Affected Products

1 product · 4 configurations

Application

controlleraviatrix

≥ 6.5 && < 6.5.1922

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.