CVE-2021-42023

lowpriority · track · 36EPSS 0.006 · 48 %ileexploit · PoCDEEUUS
grimoire priorityP1 · Urgent
Exploitable?
Public exploit
1 exploit · PoC
Likely / severe?
0.58% (48th) EPSS
CVSS 2.1 · low
Is it mine?
10 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · cisa_csaf_ot · nvd

EPSS · scored 2026-10-27

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.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

  • FixedModelSim Simulationsiemens_psirt

    Update to new releases as they become available (see also section Additional Information)

    https://support.sw.siemens.com/en-US/product/852852093/
  • FixedQuesta Simulationsiemens_psirt

    Update to new releases as they become available (see also section Additional Information)

    https://support.sw.siemens.com/en-US/product/852852103/
  • FixedModelSim Simulationcisa_csaf_ot

    Siemens recommends upgrading to the lastest version of the following product, login is required: ModelSim Simulation new releases.

    https://support.sw.siemens.com/en-US/product/852852093/
  • FixedQuesta Simulationcisa_csaf_ot

    Siemens recommends upgrading to the lastest version of the following product, login is required: Questa Simulation new releases.

    https://support.sw.siemens.com/en-US/product/852852103/
  • MitigationModelSim Simulationsiemens_psirt

    Companies that deliver encrypted design IP data to their customers: ensure that procedural and contractual measures are in place that minimize the risk of unauthorized access to the data.

  • MitigationQuesta Simulationsiemens_psirt

    Companies that deliver encrypted design IP data to their customers: ensure that procedural and contractual measures are in place that minimize the risk of unauthorized access to the data.

  • MitigationModelSim Simulationcisa_csaf_ot

    Companies that deliver encrypted design IP data to their customers: Ensure procedural and contractual measures are in place that minimize the risk of unauthorized access to the data.

  • MitigationQuesta Simulationcisa_csaf_ot

    Companies that deliver encrypted design IP data to their customers: Ensure procedural and contractual measures are in place that minimize the risk of unauthorized access to the data.

02

cvss

Technical severity, 0–10. One row per scoring source.

9.0
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–critical · 2.1–9

v2.02.1lowAV:L/AC:L/Au:N/C:P/I:N/A:Nprimary · NVD / NIST USexploitability 3.9 · impact 2.9
v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 3.6
v3.09criticalCVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:Nsecondary · CISA US
v3.19criticalCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:P/RL:U/RC:Csecondary · Siemens ProductCERT DE
v3.16.2mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:Psecondary · CVSS-BT (t0sche)
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-522USCWE-522USCWE-522US
04

exploits (1)

Public proof-of-concept and weaponised exploit code.

05

affected products (10)

Products and version ranges known to be affected.

06

advisories (2)

Vendor and ecosystem advisories describing this.

  • SSA-400332SSA-400332: Insufficient Design IP Protection in IEEE 1735 Recommended Practice - Impact to Questa and ModelSim2021-12-14csaf · siemens_psirtDE

    A security research [1] identified weaknesses in the IEEE 1735 recommended practice for encryption of Design IP, which could allow a sophisticated attacker access to unencrypted Design IP data in IEEE 1735-compliant products. This advisory addresses the specific details for the affected Siemens software products: Questa and ModelSim simulators. Siemens is preparing updates and recommends specific countermeasures for Questa and ModelSim. [1] https://arxiv.org/abs/2112.04838

  • ICSA-21-350-13Siemens Questa and ModelSim2021-12-16icsa · cisa_csaf_otUS

    Successful exploitation of this vulnerability could allow access to unencrypted data.

07

also known as (3)

Other names and identifiers for this entity.

08

sources

Which sources assert this record, and when.

cnnvdenisa_euvdcisa_csaf_otnvdsiemens_psirtNVDCVE.orgMITRE
published 2021-12-14modified 2026-06-17
09

references (6)

External citations — patches, advisories, analysis.

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