The corporate behemoth is publishing something that I get to use for free. It has a bug, that I just happen to trip over constantly. It's important to me to fix

The corporate behemoth is publishing something that I get to use for free. It has a bug, that I just happen to trip over constantly. It's important to me to fix it since it requires effort to work around it. It's just not high enough in their priority list that I can expect that to happen soon. The fix is simple and I have a good idea how to approach it. What do I do? Fork, carry the patchset until they fix it? Or contribute the fix, taking all the burden of maintaining it. I can now freely decide to accept their terms on how to contribute a change that benefits me to a project they own.