UBR-01 Mk II: Inclusion of Undocumented Features or Chicken Bits
CVE-2025-41756 is a high-severity inclusion of undocumented features or chicken bits vulnerability in UBR-01 Mk II from MBS, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 6.0.1.0 as the first without the flaw, so updating UBR-01 Mk II to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.37% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update UBR-01 Mk II to 6.0.1.0 or a later version.
- Update UBR-02 to 6.0.1.0 or a later version.
- Update UBR-LON to 6.0.1.0 or a later version.
- Read the advisory on mbs-solutions.de for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| MBS | UBR-01 Mk II | before 6.0.1.0 | 6.0.1.0 |
| MBS | UBR-02 | before 6.0.1.0 | 6.0.1.0 |
| MBS | UBR-LON | before 6.0.1.0 | 6.0.1.0 |
| Mbs-solutions | Universal Bacnet Router Firmware | before 6.0.1.0 | 6.0.1.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H. Scored by CNA (cert.vde.com).
Official description
A low-privileged remote attacker can exploit the ubr-editfile method in wwwubr.cgi, an undocumented and unused API endpoint to write arbitrary files on the system.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inclusion of Undocumented Features or Chicken Bits
The device includes chicken bits or undocumented features that can create entry points for unauthorized actors.
How developers prevent this class of flaw
- The implementation of chicken bits in a released product is highly discouraged. If implemented at all, ensure that they are disabled in production devices. All interfaces to a device should be documented.
More Inclusion of Undocumented Features or Chicken Bits vulnerabilities (CWE-1242)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in UBR-01 Mk II
- 7.5 High severity
- 7.2 High severity
- 8.8 High severity
- 9.1 Critical severity
- 9.1 Critical severity
- 7.8 High severity
Recent Inclusion of Undocumented Features or Chicken Bits vulnerabilities
- 9.8 Critical severity
- 7.5 High severity
- 7.2 High severity
- 7.5 High severity
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