Published: 08 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.
CVSS 3 base score: 7.5
Launchpad, Ubuntu, Debian
|Ubuntu 21.10 (Impish Indri)||
|Ubuntu 21.04 (Hirsute Hippo)||
|Ubuntu 20.04 LTS (Focal Fossa)||
|Ubuntu 18.04 LTS (Bionic Beaver)||
|Ubuntu 16.04 ESM (Xenial Xerus)||
|Ubuntu 14.04 ESM (Trusty Tahr)||
Does not exist
Upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=e8b7f10be275bcedb5fc05ed4837a89bfd605c61 (1.9x)
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.