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CVE-2021-40528

Published: 6 September 2021

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.

Notes

AuthorNote
mdeslaur
The commits below reference CVE-2021-33560, but they appear to
actually be for this CVE, which was issued later. The original
CVE was switched later on to the exponent blinding issue
instead.
Priority

Medium

CVSS 3 base score: 5.9

Status

Package Release Status
libgcrypt20
Launchpad, Ubuntu, Debian
bionic
Released (1.8.1-4ubuntu1.3)
focal
Released (1.8.5-5ubuntu1.1)
hirsute
Released (1.8.7-2ubuntu2.1)
impish
Released (1.8.7-5ubuntu2)
jammy
Released (1.8.7-5ubuntu2)
trusty Does not exist

upstream
Released (1.9.4-2)
xenial
Released (1.6.5-2ubuntu0.6+esm1)
Patches:
upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=3462280f2e23e16adf3ed5176e0f2413d8861320 (1.9x)
upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=707c3c5c511ee70ad0e39ec613471f665305fbea (1.8x)