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CVE-2020-27631

27
FAUCET Score

CVE-2020-27631 describes a critical vulnerability in Oryx CycloneTCP 1.9.6, where TCP Initial Sequence Numbers (ISNs) are improperly randomized, affecting embedded systems utilizing this TCP/IP stack. This flaw carries a CVSS score of 9.8 (Critical), indicating it can be exploited remotely with low complexity, potentially leading to complete compromise of confidentiality, integrity, and availability. While there is no known active exploitation, public exploit code, or KEV listing, the vulnerability has garnered some community discussion and media attention, highlighting its potential for TCP connection hijacking and spoofing.

Impacted Technologies

VendorProductVersion(s)CPE
1.9.6CPE matchmatch criteria
cpe:2.3:a:oryx-embedded:cyclonetcp:1.9.6:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.08%
Probability of exploitation in next 30 days
EPSS Percentile
61.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0108 is in the 47th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / news-events/ics-advisories/icsa-21-042-01
Third Party AdvisoryUS Government Resource
forescout.com
Third Party Advisory
forescout.com / resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks
Third Party Advisory