Cybersecurity agencies from Australia, Canada, New Zealand, the U.S., and the U.K. on Wednesday released a joint advisory in response to widespread exploitation of multiple vulnerabilities in Apache’s Log4j software library by nefarious adversaries.

“These vulnerabilities, especially Log4Shell, are severe,” the intelligence agencies said in the new guidance. “Sophisticated cyber threat actors are actively scanning networks to potentially exploit Log4Shell, CVE-2021–45046, and CVE-2021–45105 in vulnerable systems. These vulnerabilities are likely to be exploited over an extended period.”