A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions <
A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20), APOGEE PXC Modular (BACnet) (All versions < V3.5.5), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20), Nucleus NET (All versions < V5.2), Nucleus ReadyStart V3 (All versions < V2012.12), Nucleus Source Code (All versions), PLUSCONTROL 1st Gen (All versions), TALON TC Compact (BACnet) (All versions < V3.5.5), TALON TC Modular (BACnet) (All versions < V3.5.5). Initial Sequence Numbers (ISNs) for TCP connections are derived from an insufficiently random source. As a result, the ISN of current and future TCP connections could be predictable. An attacker could hijack existing sessions or spoof future ones.
- Published
- Feb 9, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.4% · 71th percentile
- CWE
- CWE-342
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Report tools
Action score
21
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.4%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 5.3
- CNA · siemens
- 6.5
- 1.2 point gap
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:O/RC:C
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| siemens | capital vstar | cpe:2.3:a:siemens:capital_vstar |
| siemens | nucleus net | cpe:2.3:a:siemens:nucleus_net |
| siemens | nucleus source code | cpe:2.3:a:siemens:nucleus_source_code |
| siemens | pluscontrol 1st gen | cpe:2.3:a:siemens:pluscontrol_1st_gen |
| siemens | nucleus readystart | cpe:2.3:a:siemens:nucleus_readystart |
| arm | arm | cpe:2.3:h:arm:arm |
| mips | mips | cpe:2.3:h:mips:mips |
| powerpc project | powerpc | cpe:2.3:h:powerpc_project:powerpc |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- siemens capital vstarall versions
- siemens nucleus netbefore 5.2
- siemens nucleus readystartbefore 2012.12
- siemens nucleus source codeall versions
- siemens pluscontrol 1st genall versions
Versions reported by the vendor
Affected version ranges reported by the assigning authority (siemens). Independent of NVD's CPE analysis and usually ahead of it.
Siemens APOGEE PXC Compact (BACnet)
- All versions < V3.5.5affected
Siemens APOGEE PXC Compact (P2 Ethernet)
- All versions < V2.8.20affected
Siemens APOGEE PXC Modular (BACnet)
- All versions < V3.5.5affected
Siemens APOGEE PXC Modular (P2 Ethernet)
- All versions < V2.8.20affected
Siemens Nucleus NET
- All versions < V5.2affected
Siemens Nucleus ReadyStart V3
- All versions < V2012.12affected
Siemens Nucleus Source Code
- All versionsaffected
Siemens PLUSCONTROL 1st Gen
- All versionsaffected
Siemens TALON TC Compact (BACnet)
- All versions < V3.5.5affected
Siemens TALON TC Modular (BACnet)
- All versions < V3.5.5affected
Same product
siemens: all recordsOther highest-scoring records for the same primary product.
- CVE-2021-31884A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (39Monitor
- CVE-2021-31890A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions 37Monitor
- CVE-2021-31889A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions 37Monitor
- CVE-2021-31346A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions 37Monitor
- CVE-2021-31345A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions 36Monitor
- CVE-2021-25664A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions 35Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-342 · Predictable Exact Value from Previous ValuesCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
- cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf
- cert-portal.siemens.com/productcert/pdf/ssa-344238.pdf
- cert-portal.siemens.com/productcert/pdf/ssa-362164.pdf
- cert-portal.siemens.com/productcert/pdf/ssa-436469.pdf
Vendor advisories and official records. Exploit/PoC links are deliberately left out.