Regarding the buffer overflow when saving some maps in Quakespasm, it's triggered by an extra long value (>512 chars) for the "wad" worldspawn key on some of the maps. It's patched in Quakespasm SVN r1607 but not released: https://sourceforge.net/p/quakespasm/code/1607/ I think the buffer overflow is present in the original engine as well so it'll affect anything that doesn't patch this.
Since it's a buffer overflow, it may or may not crash for you. Maps should avoid extra long keys, ideally the compile tools would warn about this, etc.
Unfortunately I don't have linux binaries of the latest SVN code to offer but if you can build Quakespasm SVN from source that would be worth a try, otherwise Spirit's advice is good.
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