Is CVE-2021-21777 actively exploited?

No active exploitation of CVE-2021-21777 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-21777 be exploited remotely?

Yes. CVE-2021-21777 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-21777?

CVE-2021-21777 has a CVSS score of 10.0 (CRITICAL).

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CRITICAL

CVE-2021-21777

CWE-125Published: June 17, 2021· Updated: Jun 17, 2026

10.0

CVSS v3.1

Official Description

An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. A specially crafted network request can lead to an out-of-bounds read.

NVD Source

Technical Analysis

CVE-2021-21777 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), availability disruption (denial of service), with a CVSS base score of 10.0.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.