This indicates an attack attempt to exploit a Buffer Overflow Vulnerability in ZLib Compression Library.
The vulnerability is due to input validation error when processing gzip files. A remote attacker can exploit this vulnerability by sending a crafted request or file to a target application. Successful exploitation could result in arbitrary code execution in the context of the target application.
zlib Software ZLib Compression Library 1.2.12 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.