The listed shared library in a public library directory has an SONAME that does not contain any versioning information, either after the .so or before it and set off by a hyphen. It cannot therefore be represented in the shlibs system, and if linked by binaries its interface cannot safely change. There is no backward-compatible way to migrate programs linked against it to a new ABI.
Normally, this means the shared library is a private library for a particular application and is not meant for general use. Policy recommends that such libraries be installed in a subdirectory of /usr/lib rather than in a public shared library directory.
To view the SONAME of a shared library, run readelf -d on the shared library and look for the tag of type SONAME.
There are some special stub libraries or special-purpose shared objects for which an ABI version is not meaningful. If this is one of those cases, please add an override.
Refer to Debian Policy Manual section 10.2 (Libraries) and Debian Policy Manual section 8.6 (Dependencies between the library and other packages) for details.