SAN FRANCISCO — Billions of devices—many of them already patched—are affected by a Wi-Fi vulnerability that allows nearby attackers to decrypt sensitive data sent over the air, researchers said on Wednesday at the RSA security conference.

The vulnerability exists in Wi-Fi chips made by Cypress Semiconductor and Broadcom, the latter a chipmaker Cypress acquired in 2016. The affected devices include iPhones, iPads, Macs, Amazon Echos and Kindles, Android devices, Raspberry Pi 3’s, and Wi-Fi routers from Asus and Huawei. Eset, the security company that discovered the vulnerability, said the flaw primarily affects Cyperess’ and Broadcom’s FullMAC WLAN chips, which are used in billions of devices. Eset has named the vulnerability Kr00k, and it is tracked as CVE-2019-15126.

Manufacturers have made patches available for most or all of the affected devices, but it’s not clear how many devices have installed the patches. Of greatest concern are vulnerable wireless routers, which often go unpatched indefinitely.