The Sächsische Landesbibliothek – Staats- und Universitätsbibliothek Dresden (Saxon State and University Library Dresden), which somehow gets abbreviated to SLUB, has developed a tool for working with TIFF files in digital preservation. fixit_tiff is a command line utility, written in C, which can do some repairs on defective TIFF files. The focus appears to be on correcting common errors, not on repairing corrupted files. A blog post from July (in German) indicates it can do configurable validation using a simple query language.
It’s available under the same license as Libtiff. Just what is that license? The only thing I can find is a very outdated “Use and Copyright” statement, which is on a page so old it warns about patents on LZW compression. It’s available for free, anyway.