CVE-2015-3963
MEDIUMEPSS 89th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
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
Elevated risk: more likely to be exploited than 89% of all known CVEs.
References
Related Vulnerabilities
Other CWE-330 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-5420 | Critical | 9.8 | 92% | - | Fix |
| CVE-2021-34646 | Critical | 9.8 | 51% | - | - |
| CVE-2008-0087 | High | 7.5 | 32% | - | - |
| CVE-2017-6026 | Critical | 9.1 | 32% | - | - |
| CVE-2018-17888 | Critical | 9.8 | 30% | - | - |
| CVE-2020-11901 | Critical | 9.0 | 21% | - | Fix |
Common questions
How do I fix CVE-2015-3963?
Upgrade vxworks to 6.9.4.4 or later.
Is CVE-2015-3963 being actively exploited?
Not that we know of. CVE-2015-3963 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 3.7% is the estimated probability that it will be exploited in the next 30 days. That is higher than 89% of all scored CVEs.
How severe is CVE-2015-3963?
CVE-2015-3963 has a CVSS v2 base score of 5.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2015-3963 affect?
Published advisories record a fix for vxworks (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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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.