CVE-2021-40528

MEDIUM

libgcrypt < 1.9.4 - Plaintext Recovery via ElGamal Cross-Configuration Attack

Title source: llm

Description

The ElGamal implementation in Libgcrypt before 1.9.4 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.

References (5)

Core 5

Core References

Third Party Advisory vendor-advisory

https://security.gentoo.org/glsa/202210-13

Technical Description, Third Party Advisory

https://eprint.iacr.org/2021/923

Third Party Advisory

https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1

Exploit, Third Party Advisory

https://ibm.github.io/system-security-research-updates/2021/09/06/insecurity-elgamal-pt2

Various Sources

https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git%3Ba=commit%3Bh=3462280f2e23e16adf3ed5176e0f2413d8861320

Scores

CVSS v3 5.9

EPSS 0.0132

EPSS Percentile 67.1%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-327

Status published

Products (1)

gnupg/libgcrypt < 1.9.4

Published Sep 06, 2021

Tracked Since Feb 18, 2026