jdk8u

Would an atomic mutable subclass cache (not sure what it's used for, downcasting?) be unnecessary in a language built around static rather than dynamic dispatch by default, like C/C++/Rust and perhaps Go? Or would it still speed up dynamically dispatched code, but is less practical or worthwhile so it isn't used in practice? (Though Rust's Arc also suffers from atomic contention similar to this blog post, when used across dozens of threads: https://pkolaczk.github.io/server-slower-than-a-laptop/) Also it's somewhat ironic that the JVM source code (https://github.com/openjdk/jdk8u/blob/jdk8u352-b07/hotspot/s...) says "This code is rarely used, so simplicity is a virtue here" at the site of a bottleneck.

> whatever it returned would just get inserted as a string into the log output, no big deal. Once you can inject anything that gets resolved, you have an information disclosure vulnerability unrelated to the RCE. If I can just DNS resolve any ${env} variable from the JVM, a lot of systems are compromised by just exposing the env or system variables configured for runtime. Just getting your $AWS_ACCESS_KEY_ID and $AWS_SECRET_ACCESS_KEY env vars can compromise your bucket (sure, that is a really unsafe setup now, but it was almost the standard a few years ago over configuring it explicitly). So a logging system which will merely resolve a hostname derived from a variable was bad enough to compromise many systems. The serialization loophole was fixed in a jdk8 update. https://github.com/openjdk/jdk8u/commit/006e84fc77a582552e71... But even w

> Turns out, by including "." in some part of the URL to this remote class, Log4j lets off its guard & simply looks up to that server and dynamically loads the class file. No it doesn't. That was disabled by default in 2009, and was disabled by default in every release of Java 8 or later: https://github.com/openjdk/jdk8u/commit/006e84fc77a582552e71... Unless i am mistaken, i don't believe the attack as described by LunaSec actually works against a default-configured JVM released any time in the last decade.

The trustURLCodebase check was added to the LDAP provider in 2009: https://github.com/openjdk/jdk8u/commit/006e84fc77a582552e71... This change is included in tag jdk8-b01, which was the first release build of Java 8. I don't think this exploit as described actually works against a default-configured JVM released any time in the last decade. Is there actually an executable PoC which shows otherwise? Now, it's true there are ways to exploit deserialisation without loading code. You need to find a class in the classpath that does something sketchy when deserialised. There has been a lot of work to clean up such things in recent years, but it's possible some still exist. Again, i would like to see a PoC.