What’s Vulnerable › Vulnerabilities

CVE-2021-25663

• Severity: medium (CVSS 5.0 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-04-22 · updated 2026-06-17
• Weakness: CWE-835

Description

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus ReadyStart V4 (All versions < V4.1.0), Nucleus Source Code (All versions including affected IPv6 stack). The function that processes IPv6 headers does not check the lengths of extension header options, allowing attackers to put this function into an infinite loop with crafted length values.

Affected products

• Siemens Capital VSTAR: all versions
• Siemens Nucleus NET: all versions
• Siemens Nucleus Readystart: before 4.1.0; before 2017.02.4 — fixed in 2017.02.4, 4.1.0
• Siemens Nucleus Source Code: all versions

How to fix

Upgrade to a fixed version: Siemens Nucleus Readystart 2017.02.4, 4.1.0. Check the vendor advisory for mitigations.

References

• https://cert-portal.siemens.com/productcert/html/ssa-248289.html
• https://cert-portal.siemens.com/productcert/pdf/ssa-248289.pdf
• https://us-cert.cisa.gov/ics/advisories/icsa-21-103-05
• https://cert-portal.siemens.com/productcert/html/ssa-248289.html
• https://cert-portal.siemens.com/productcert/pdf/ssa-248289.pdf
• https://us-cert.cisa.gov/ics/advisories/icsa-21-103-05

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