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CVE Record

CVE-2021-40529: The ElGamal implementation in Botan through 2.18.1, as used in Thunderbird and other products, allows plain...

The ElGamal implementation in Botan through 2.18.1, as used in Thunderbird and other products, 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 analysishigh

Security readout for executives and security teams

Plain-English summary

This issue can undermine confidentiality for encrypted OpenPGP messages when Botan's ElGamal implementation is used in vulnerable conditions. The reported impact is plaintext recovery, meaning encrypted content may become readable. The source data names Botan through 2.18.1 and mentions Thunderbird and other products, but the affected-product inventory is incomplete.

Executive priority

Treat this as a confidentiality risk for encrypted communications, especially in environments using OpenPGP. Prioritize inventory and vendor updates, but do not assume broad exposure without confirming Botan usage and affected cryptographic paths.

Technical view

CVE-2021-40529 describes a cross-configuration attack against OpenPGP involving Botan's ElGamal implementation through 2.18.1. A dangerous combination of receiver public-key parameters and sender ephemeral exponents can permit plaintext recovery during interaction between two cryptographic libraries. CVSS and CWE data were not supplied.

Likely exposure

Most likely exposure is software using Botan through 2.18.1 for ElGamal/OpenPGP operations. The description mentions Thunderbird and other products, but the provided affected list is generic and does not enumerate vendors, versions, or CPEs.

Exploitation context

The bundle does not show CISA KEV listing or active exploitation evidence. The risk is cryptographic and message-confidentiality focused. Practical exposure depends on whether vulnerable Botan ElGamal/OpenPGP paths are present and reachable in deployed software.

Researcher notes

The strongest source details are the CVE description, IBM research posts, IACR paper, and Botan pull request. Affected-product metadata is incomplete, so exposure claims should stay limited to Botan through 2.18.1 and named downstream examples.

Mitigation direction

  • Inventory Botan versions in applications and system packages.
  • Update Botan and distribution packages using vendor advisories.
  • Check Thunderbird or product vendor guidance where Botan/OpenPGP is embedded.
  • Avoid relying on ElGamal/OpenPGP paths using vulnerable Botan releases.
  • Track Fedora, Gentoo, and Botan upstream notices for fixed package details.

Validation and detection

  • Confirm whether Botan through 2.18.1 exists in runtime or build dependencies.
  • Identify applications using Botan for OpenPGP or ElGamal operations.
  • Review package advisories for installed Fedora or Gentoo systems.
  • Verify updated packages replace vulnerable Botan builds.
  • Document any products where embedded Botan version cannot be confirmed.
Prepared
Confidence
medium
Sources
9

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-40529 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
8Source 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.