BIT-fluent-bit-2024-50608

An issue was discovered in Fluent Bit 3.1.9. When the Prometheus Remote Write input plugin is running and listening on an IP address and port, one can send a packet with Content-Length: 0 and it crashes the server. Improper handling of the case when Content-Length is 0 allows a user (with access to the endpoint) to perform a remote Denial of service attack. The crash happens because of a NULL pointer dereference when 0 (from the Content-Length) is passed to the function cflsdslen, which in turn tries to cast a NULL pointer into struct cflsds. This is related to processpayloadmetricsng() at promrwprot.c.