Hi! I got following “invalid signature error” on kali linux when trying to update using apt-get update command. Below I list down the working solution for me among various solutions on forums.

Error:

W: GPG error: https://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.6 Release: The following signatures were invalid: EXPKEYSIG 58712A2291FA4AD5 MongoDB 3.6 Release Signing Key <packaging@mongodb.com>
E: The repository 'https://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.6 Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Solution:

Use following sequence of commands.

• sudo rm -rf /var/lib/apt/lists

• sudo mkdir -p /var/lib/apt/lists/partial

• sudo apt-get clean

• sudo apt-get update

“invalid: EXPKEYSIG 58712A2291FA4AD5 MongoDB 3.6 Release Sign” from the error message above.

• sudo apt-key adv --recv-keys --keyserver keys.gnupg.net 91FA4AD5

• apt-get update

Console output:

Cheers! 🙂