How severe is CVE-2021-21978?

CVE-2021-21978 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which products are affected by CVE-2021-21978?

Affected package information for CVE-2021-21978 is not yet fully mapped. Check the official advisory links for details.

How do I patch CVE-2021-21978?

Apply the vmware view planner security patch or hotfix for CVE-2021-21978 on the affected version, following the vendor advisory for your exact build.

How do I detect CVE-2021-21978 across my infrastructure?

Inventory every vmware view planner deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

How do I mitigate CVE-2021-21978 if there is no patch (or I can't update yet)?

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2021-21978?

O3 detects and blocks CVE-2021-21978 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Is CVE-2021-21978 actively exploited in the wild?

Yes. There are 8 known exploit references for CVE-2021-21978, including 5 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-2021-21978?

CVE-2021-21978 has an EPSS (Exploit Prediction Scoring System) score of 99.0%, 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.

What type of vulnerability is CVE-2021-21978?

CVE-2021-21978 is classified as Improper Input Validation (CWE-20), CWE-862 (CWE-862). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2021-21978?

CVE-2021-21978 affects vmware view planner (1 version, e.g. 4.6). Check the affected-products list on this page against your deployed version to confirm exposure.

Is there exploit tooling available for CVE-2021-21978?

A Nuclei detection template exists for CVE-2021-21978, 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-2021-21978 published, and has it been updated?

CVE-2021-21978 was published on March 3, 2021 and was last updated on June 17, 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-2021-21978

CRITICAL

VMware View Planner 4.x prior to 4.6 Security Patch 1 contains a remote code execution vulnerability. Improper input validation and lack of authorization leading to arbitrary file upload…

Published

Mar 3, 2021

Updated

Jun 17, 2026

Affected

0 pkgs

Patched

None yet

Exploits

8 known

EPSS Exploitation Probability

via FIRST.org ↗

99.0%probability of exploitation in next 30 days

Very High Risk100th percentile+0.06%

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.

Description

VMware View Planner 4.x prior to 4.6 Security Patch 1 contains a remote code execution vulnerability. Improper input validation and lack of authorization leading to arbitrary file upload in logupload web application. An unauthorized attacker with network access to View Planner Harness could upload and execute a specially crafted file leading to remote code execution within the logupload container.

Affected Products

1 product · 2 configurations

Application

view plannervmware

≥ 4.0 && < 4.6

1 version

4.6

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.