Hello!

We have to announce the availability of Libgcrypt version 1.9.1.
This version fixes a *critical security bug* in the recently released
version 1.9.0.  If you are already using 1.9.0 please update immediately
to 1.9.1.

Libgcrypt is a general purpose library of cryptographic building blocks.
It is originally based on code used by GnuPG.  It does not provide any
implementation of OpenPGP or other protocols.  Thorough understanding of
applied cryptography is required to use Libgcrypt.


Impact and timeline
===================

Only one released version is affected:

 - Libgcrypt 1.9.0 (released 2021-01-19)

All other versions are not affected.

On 2021-01-28 Tavis Ormandy contacted us to report a severe bug in 1.9.0
which he found while testing GnuPG:

  There is a heap buffer overflow in libgcrypt due to an incorrect
  assumption in the block buffer management code. Just decrypting some
  data can overflow a heap buffer with attacker controlled data, no
  verification or signature is validated before the vulnerability
  occurs.

The bug was introduced during the the 1.9 development phase about two
years ago with commit e76617cbab018dd8f41fd6b4ec6740b5303f7e13 (Reduce
overhead on generic hash write function).

Exploiting this bug is simple and thus immediate action for 1.9.0 users
is required.  A CVE-id has not yet been assigned.  We track this bug at
https://dev.gnupg.org/T5275.  The 1.9.0 tarballs on our FTP server have
been renamed so that scripts won't be able to get this version anymore.


Solution
========

If Libgcrypt versions 1.9.0 is in use please update immediately to
version 1.9.1.

If you are using the 1.8 LTS branch you are not affected.  While you are
checking anyway please make sure that you have at least 1.8.5.

If you are using a development version build taken from our Git
repository you need to update as well.  NB: The use of non-released
versions in a production environment is strongly discouraged.

There is yet no released GnuPG version hich requires Libgcrypt 1.9

References
https://bugs.chromium.org/p/project-zero/issues/detail?id=2145
https://lists.gnupg.org/pipermail/gnupg-announce/2021q1/000455.html
https://lists.gnupg.org/pipermail/gnupg-announce/2021q1/000456.html
https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=512c0c75276949f13b6373b5c04f7065af750b08