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CVE Record

CVE-2021-40530: The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction be...

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Crypto++ ElGamal through 8.5 can expose encrypted plaintext in a narrow interoperability scenario involving OpenPGP and another cryptographic library. This is a confidentiality issue, not a broad remote-code-execution flaw. Business urgency depends on whether systems use Crypto++ ElGamal/OpenPGP handling for sensitive data.

Executive priority

Treat as targeted confidentiality risk. Prioritize systems that encrypt sensitive messages or files using Crypto++ ElGamal/OpenPGP. If that usage is absent, urgency is lower, but dependency inventory should still be verified.

Technical view

The CVE describes plaintext recovery caused by a dangerous combination of receiver public-key parameters and sender ephemeral exponents during cross-library interaction. The issue is tied to ElGamal behavior in Crypto++ through 8.5 and a cross-configuration attack against OpenPGP. The source bundle provides no CVSS vector or CWE.

Likely exposure

Exposure is most likely in applications or distributions using Crypto++ ElGamal through 8.5 for OpenPGP-related encryption workflows. General Crypto++ users may not be affected if they do not use this algorithm or interoperability path. The affected CPE list is incomplete.

Exploitation context

The bundle cites academic and IBM research plus Fedora advisories, but KEV is false and no source states active exploitation. Exploitation appears to require specific cryptographic parameter interactions rather than simple unauthenticated scanning.

Researcher notes

Evidence supports a cryptographic plaintext-recovery issue under specialized cross-configuration conditions. The bundle does not include exploit proof, CVSS, CWE, complete affected CPEs, or exact fixed release details beyond Fedora advisory references and Crypto++ through 8.5 wording.

Mitigation direction

  • Identify systems using Crypto++ ElGamal or OpenPGP integrations.
  • Update Crypto++ packages according to vendor or distribution advisories.
  • Review Fedora advisories if using affected Fedora packages.
  • Avoid assuming unrelated Crypto++ usage is exposed without algorithm confirmation.
  • Check upstream Crypto++ guidance for fixed versions and migration notes.

Validation and detection

  • Inventory Crypto++ versions and package sources across applications and hosts.
  • Confirm whether ElGamal and OpenPGP workflows are actually used.
  • Review cryptographic interoperability paths involving multiple libraries.
  • Check vendor advisories for package update status.
  • Document any systems retaining Crypto++ through 8.5.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-40530 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.