I don't understand why major.minor.patchlevel is a "hint". It had been an interface contract with shared libraries written in C when I first touched Linux, and that was 25+ years ago; way before the term "semantic version" was even invented (AFAICT).
Imagine I make a library for loading a certain format of small, trusted configuration files.
Some guy files a CVE against my library, saying it crashes if you feed it a large, untrusted file.
I decide to put out a new version of the library, fixing the CVE by refusing to load conspicuously large files. The API otherwise remains unchanged.
Is the new release a major, minor, or bugfix release? As I have only an approximate understanding of semantic versioning norms, I could go for any of them to be honest.
Some other library authors are just as confused as me, which is why major.minor.patchlevel is only a hint.
The client who didn't notice a difference would probably call it a bugfix.
The client whose software got ever-so-slightly more reliable probably would call it a minor update.
The client whose software previously was loading large files (luckily) without issue would call it major, because now their software just doesn't work anymore.
It's also an almost-real situation (although I wasn't the library developer involved)
You can Google "YAMLException: The incoming YAML document exceeds the limit" - an error introduced in response to CVE-2022-38752 - to see what happens when a library introduces a new input size limit.
What happened in that case is: the updated library bumps their version from 1.31 to 1.32; then a downstream application updates their dependencies, passes all tests, and updates their version from 9.3.8.0 to 9.3.9.0
> Imagine I make a library for loading a certain format of small, trusted configuration files.
> Some guy files a CVE against my library, saying it crashes if you feed it a large, untrusted file.
Not CVE-worthy, as the use case clearly falls outside of the documented / declared area of application.
> refusing to load conspicuously large files [...] Is the new release a major, minor, or bugfix release?
It deserves a major release, because it breaks compatibility. A capability that used to work (i.e,. loading a large but trusted file) no longer works. It may not affect everyone, but when assessing impact, we go for the most conservative evaluation.
