Apache 2.4.9 affected, but the selector only allows me to flag 2.4.7. When I do a GET of a resource with "accept-encoding: gzip", I get a compressed version and a ETAG like "2bc8-4f63627bade04-gzip". If time after that I repeat the request with If-None-Match: "2bc8-4f63627bade04-gzip" I get a 200 again!, sending the content back again. If, instead, I do a: If-None-Match: "2bc8-4f63627bade04" I get the correct 304, no changes. So, looks like Apache is adding "-gzip" suffix to the ETAG, but it is not verifying it when it gets a "If-Modified-Since".
*** This bug has been marked as a duplicate of bug 45023 ***