Early yesterday morning a collection of major vulnerabilities in most implementations of WPA2 was made public. The impact of this set of attacks, known as KRACK (Key Reinstallation Attack) is severe, allowing decryption of wireless traffic and, in some cases, traffic modification. You can find out more details on this attack at the website created by the discoverer and in the research paper Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2. Cisco is beginning to release updated firmware for their affected products. You can use this CERT page to find security updates from all the different impacted vendors.