variTRON300: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
CVE-2025-41731 is a high-severity use of cryptographically weak pseudo-random number generator (PRNG) vulnerability in variTRON300 from Jumo, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists version 9.0.2.5 as the first without the flaw, so updating variTRON300 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% 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 variTRON300 to 9.0.2.5 or a later version.
- Update variTRON500 to 9.0.2.5 or a later version.
- Update variTRON500 touch to 9.0.2.5 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Jumo | variTRON300 | 0.0.0.0 up to, but not including, 9.0.2.5 | 9.0.2.5 |
| Jumo | variTRON500 | 0.0.0.0 up to, but not including, 9.0.2.5 | 9.0.2.5 |
| Jumo | variTRON500 touch | 0.0.0.0 up to, but not including, 9.0.2.5 | 9.0.2.5 |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (cert.vde.com).
Official description
A vulnerability was identified in the password generation algorithm when accessing the debug-interface. An unauthenticated local attacker with knowledge of the password generation timeframe might be able to brute force the password in a timely manner and thus gain root access to the device if the debug interface is still enabled.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.
How developers prevent this class of flaw
- Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
More Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) vulnerabilities (CWE-338)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Recent Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) vulnerabilities
- 9.1 Critical severity
- 7.5 High severity
- 8.6 High severity
- 9.3 Critical severity
- 9.8 Critical severity
- 7.3 High severity
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