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CVE-2021-33560

Published: 8 June 2021

Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm, and the window size is not chosen appropriately. This, for example, affects use of ElGamal in OpenPGP.

Notes

AuthorNote
mdeslaur
This CVE was originally for the issue that is now CVE=2021-40528
but somehow got switched to the exponent blinding issue instead.
The fix to add exponent blinding appears to only have been added
to 1.9.x but never backported to 1.8.x, contrary to the CVE
description
The commit below was never backported to 1.8.x because the
upstream developers consider this hardening and not a security
issue.
Priority

Low

CVSS 3 base score: 7.5

Status

Package Release Status
libgcrypt20
Launchpad, Ubuntu, Debian
bionic
Released (1.8.1-4ubuntu1.3)
focal
Released (1.8.5-5ubuntu1.1)
groovy Ignored
(reached end-of-life)
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 (1.8.7-6)
xenial
Released (1.6.5-2ubuntu0.6+esm1)
Patches:
upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=e8b7f10be275bcedb5fc05ed4837a89bfd605c61 (1.9x)