The tag is present in Lintian version 2.109.24. That is the most recent version we know about.
The listed shared library lacks a PT_GNU_STACK section. This forces the dynamic linker to make the stack executable.
The shared lib is linked either with a non-GNU linker or a linker which is very old. This problem can be fixed with a rebuild.
To see whether a shared library has this section, run
on it and look for a program header of type GNU_STACK.