CVE-2021-42023Public exploit

Design IP disclosure via extractable embedded RSA keys

Published Dec 14, 2021 · Updated Aug 4, 2024

Insufficient key protection in all versions of Siemens ModelSim and Questa allows local users to decrypt protected electronic design IP. The CRT-RSA white-box stores algebraically related split parameters whose reconstruction permits modulus factorization and recovery of its private exponent. An attacker must obtain and reverse engineer the installed software; recovered keys permit decryption, modification, and re-encryption of IEEE 1735 IP protected for those keys.

CVSS severity6.5
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient key protection in all versions of Siemens ModelSim and Questa allows local users to decrypt protected electronic design IP. The CRT-RSA white-box stores algebraically related split parameters whose reconstruction permits modulus factorization and recovery of its private exponent. An attacker must obtain and reverse engineer the installed software; recovered keys permit decryption, modification, and re-encryption of IEEE 1735 IP protected for those keys.

The record

CVE
CVE-2021-42023
Published
Dec 14, 2021
Updated
Aug 4, 2024
Vendor
Siemens
Product
Questa
Classifications
CWE-522, T1140
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=All versions

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Siemens · Questaversion=All versions
Siemens · ModelSimversion=All versions

Published CVSS scores

9.0Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:P/RL:U/RC:C
2.1NIST NVDAV:L/AC:L/Au:N/C:P/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
T1140Deobfuscate/Decode Files or Information

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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