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CVE-2021-27500

25
FAUCET Score

CVE-2021-27500 is a denial-of-service vulnerability affecting EIPStackGroup OpENer EtherNet/IP commits and versions prior to February 10, 2021. An unauthenticated attacker can exploit this by sending a specially crafted packet over the network, leading to a high-severity impact on system availability. While no public exploit code or active exploitation has been observed, the vulnerability has garnered some community discussion and media coverage. Its EPSS score suggests a low probability of exploitation, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2.3CPE matchmatch criteria
cpe:2.3:a:opener_project:opener:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.22%
Probability of exploitation in next 30 days
EPSS Percentile
65.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0122 is in the 45th percentile among its peer group of 51,553 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / EIPStackGroup/OpENer
Third Party Advisory
cisa.gov / uscert/ics/advisories/icsa-21-105-02
Third Party AdvisoryUS Government Resource