[ASA-202009-5] gnupg: arbitrary code execution

[Morten Linderud]

Arch Linux Security Advisory ASA-202009-5
=========================================

Severity: Critical
Date    : 2020-09-07
CVE-ID  : CVE-2020-25125
Package : gnupg
Type    : arbitrary code execution
Remote  : Yes
Link    : https://security.archlinux.org/AVG-1218

Summary
=======

The package gnupg before version 2.2.23-1 is vulnerable to arbitrary
code execution.

Resolution
==========

Upgrade to 2.2.23-1.

# pacman -Syu "gnupg>=2.2.23-1"

The problem has been fixed upstream in version 2.2.23.

Workaround
==========

None.

Description
===========

Importing an OpenPGP key having a preference list for AEAD algorithms
will lead to an array overflow and thus often to a crash or other
undefined behaviour.

Importing an arbitrary key can often easily be triggered by an attacker
and thus triggering this bug. Exploiting the bug aside from crashes is
not trivial but likely possible for a dedicated attacker.  The major
hurdle for an attacker is that only every second byte is under their
control with every first byte having a fixed value of 0x04.

Software distribution verification should not be affected by this bug
because such a system uses a curated list of keys.

Impact
======

A remote attacker might be able to execute arbitrary code by tricking a
legitimate user into importing a crafted OpenPGP key.

References
==========

https://lists.gnupg.org/pipermail/gnupg-announce/2020q3/000448.html
https://dev.gnupg.org/T5050
https://security.archlinux.org/CVE-2020-25125
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