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Fencer Intel
medium 6.5

CVE-2021-42023 json

A vulnerability has been identified in ModelSim Simulation (All versions), Questa Simulation (All versions).

published 4y ago modified 4mo ago also EUVD-2021-29011

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

A vulnerability has been identified in ModelSim Simulation (All versions), Questa Simulation (All versions). The RSA white-box implementation in affected applications insufficiently protects the built-in private keys that are required to decrypt electronic intellectual property (IP) data in accordance with the IEEE 1735 recommended practice. This could allow a sophisticated attacker to discover the keys, bypassing the protection intended by the IEEE 1735 recommended practice.

Patch / fix

Is CVE-2021-42023 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-21-350-13 updated cvss 9.0

Siemens Questa and ModelSim

  • Siemens ModelSim Simulation
    affected: vendor fix, mitigation “Company-internal use of encrypted design IP data: Apply technical and procedural measures to ensure access to the data is granted on a need-to-know basis.” support.sw.siemens.com
  • Siemens Questa Simulation
    affected: vendor fix, mitigation “Company-internal use of encrypted design IP data: Apply technical and procedural measures to ensure access to the data is granted on a need-to-know basis.” support.sw.siemens.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • Siemens ModelSim Simulation
  • Siemens Questa Simulation

Classification

Weakness
  • CWE-522 Insufficiently Protected Credentials

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.