Is CVE-2015-3963 in the CISA KEV catalog?

No. CVE-2015-3963 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2015-3963?

CVE-2015-3963 has a CVSS v2 base score of 5.8 (MEDIUM).

What is the EPSS score for CVE-2015-3963?

CVE-2015-3963 has an EPSS score of 3.74% (88th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2015-3963?

Upgrade vxworks to 6.9.4.4 or later.

CVE & CISA-KEV Catalog

CVE-2015-3963

MEDIUMEPSS 88th pctl

5.8

CVSS v2

NVD

Description

Wind River VxWorks before 5.5.1, 6.5.x through 6.7.x before 6.7.1.1, 6.8.x before 6.8.3, 6.9.x before 6.9.4.4, and 7.x before 7 ipnet_coreip 1.2.2.0, as used on Schneider Electric SAGE RTU devices before J2 and other devices, does not properly generate TCP initial sequence number (ISN) values, which makes it easier for remote attackers to spoof TCP sessions by predicting an ISN value.

CWE-330

How to fix

Remediation Available

vxworksNVD

Affected:>= 6.9, < 6.9.4.4Fixed in:6.9.4.4CVE-2015-3963derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v2 Vector

No CVSS vector data available.

Exploit Intelligence

3.74%probability of exploitation in 30 days

88thpercentile

Elevated risk: more likely to be exploited than 88% of all known CVEs.

References

Patch1

schneider-electric.com

Third-Party Advisory6

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-06.