From the source :
We discovered a way to inject data through the passphrase property of the gnupg.GPG.encrypt() and gnupg.GPG.decrypt() methods when symmetric encryption is used.
The supplied passphrase is not validated for newlines, and the library passes --passphrase-fd=0 to the gpg executable, which expects the passphrase on the first line of stdin, and the ciphertext to be decrypted or plaintext to be encrypted on subsequent lines.
By supplying a passphrase containing a newline an attacker can control/modify the ciphertext/plaintext being decrypted/encrypted.
Vulnerable in: python-gnupg 0.4.3 and maybe earlier versions.
Mitigation : Users should upgrade to python-gnupg 0.4.4
Created python-gnupg tracking bugs for this issue:
Affects: epel-6 [bug 1670367]
Affects: epel-7 [bug 1670368]
Affects: fedora-all [bug 1670366]
Filter out newlines from passphrases before passing them to python-gnupg.
The issue affects the versions of python-gnupg shipped with Red Hat Update Infrastructure 3, however the vulnerable functions are never used by the product.
The issue affects the versions of python-gnupg shipped with Red Hat Satellite 6, however the vulnerable functions are never used by the product.