An authenticated SSH user could pass a malformed sub-verb (e.g.
`git-lfs-authenticate <repo> badverb`) so getAccessMode falls through to
AccessModeNone (0). The permission check in routers/private/serv.go then
evaluates `userMode < 0` which is always false, granting a valid LFS JWT
for any private repository. The HTTP LFS handler only validates the Op
claim on writes, so the token works for downloads.
Validate the sub-verb in runServ before calling getAccessMode and fail
fast for anything other than upload/download.
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