ICSA-21-103-05: Siemens Nucleus Products IPv6 Stack
CISA advisory · released 2021-04-13
Source record Collected from CISA's CSAF advisory feed
- Distribution label in the document: TLP:WHITE
- Revision 4, 2025-03-11 (final)
CISA's summary
Summary: The IPv6 stack of the networking component (Nucleus NET) in Nucleus Real-Time Operating System (RTOS) contains two vulnerabilities when processing IPv6 headers which could allow an attacker to cause a denial of service condition. Siemens has released new versions for several affected products and recommends to update to the latest versions. Siemens is preparing further fix versions and recommends countermeasures for products where fixes are not, or not yet available.
Products, as the advisory lists them
| Vendor | Product | Version |
|---|---|---|
| Siemens | Capital Embedded AR Classic 431-422 | vers:all/* |
| Siemens | Capital Embedded AR Classic R20-11 | vers:all/<V2303 |
| Siemens | Nucleus NET | vers:all/* |
| Siemens | Nucleus ReadyStart V3 | vers:all/<V2017.02.4 |
| Siemens | Nucleus ReadyStart V4 | vers:all/<V4.1.0 |
| Siemens | Nucleus Source Code | vers:all/* |
DeSpy has not checked any unit, hardware revision or firmware.
Vulnerabilities in this advisory
- CVE-2021-25663 — CVE-2021-25663 · CWE-835
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.
- CVE-2021-25664 — CVE-2021-25664 · CWE-835
The function that processes the Hop-by-Hop extension header in IPv6 packets and its options lacks any checks against the length field of the header, allowing attackers to put the function into an infinite loop by supplying arbitrary length values.
Acknowledgments, as the advisory lists them
- Siemens ProductCERT: reporting these vulnerabilities to CISA.
The advisory's legal notice
The use of Siemens Security Advisories is subject to the terms and conditions listed on: https://www.siemens.com/productcert/terms-of-use.
Sources
DeSpy's copy of this version is dated 2026-09-28.
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