The remote host is missing a critical security patch or upgrade.
The remote host is using software based on a vulnerable version of the Neon Library, an open-source HTTP and WebDAV client library. It is reported that versions prior 0.24.7 contains an unspecified vulnerability. Due to the nature of the library, it is likely that this is a remotely exploitable vulnerability.
Upgrade to Neon library 0.24.7 or higher.