GnuPG (version 2.5.21) for Windows contains a vulnerability where default Discretionary Access Control List (DACL) inheritance on the C:\ProgramData directory allows members of the BUILTIN\Users group to create arbitrary subdirectories under this path. An attacker with low-privilege access can create the expected GnuPG configuration directory and inject malicious configuration files consumed by GnuPG components. This can result in code execution within the security context of the victim user.
gpgtar in GnuPG before 2.5.19 can allow file overwrite via crafted data in an archive. When extracting an untrusted archive with --directory (aka -C) into an existing directory containing a pre-existing symlink, gpgtar can follow that symlink and create or overwrite a file outside the selected extraction directory. The write is limited by the extraction user's filesystem permissions. An archive extracted into a fresh empty directory does not have this risk.
In GnuPG before 2.4.9, armor_filter in g10/armor.c has two increments of an index variable where one is intended, leading to an out-of-bounds write for crafted input. (For ExtendedLTS, 2.2.51 and later are fixed versions.)
USN-7412-1 fixed vulnerabilities in GnuPG. The update introduced a
regression. This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
It was discovered that GnuPG incorrectly handled importing keys with
certain crafted subkey data. If a user or automated system were tricked
into importing a specially crafted key, a remote attacker may prevent
users from importing other keys in the future.
In GnuPG before 2.5.5, if a user chooses to import a certificate with certain crafted subkey data that lacks a valid backsig or that has incorrect usage flags, the user loses the ability to verify signatures made from certain other signing keys, aka a "verification DoS."
GnuPG can be made to spin on a relatively small input by (for example) crafting a public key with thousands of signatures attached, compressed down to just a few KB.
GnuPG through 2.3.6, in unusual situations where an attacker possesses any secret-key information from a victim's keyring and other constraints (e.g., use of GPGME) are met, allows signature forgery via injection into the status line.