GHSA-2m9v-5q2g-58vq: Gitea: Git LFS object reuse allows non-Code access to authorize private source objects

Summary A user with Code write access to one repository may be able to associate an existing Git LFS object from a private source repository with their target repository, even when they do not have Code access to the source repository that currently owns the LFS object. The issue appears to be caused by the source-object authorization check using broad repository accessibility instead of requiring Code-unit access to at least one repository that owns the requested LFS object. Impact This issue breaks the expected authorization boundary between repository units. A user who does not have Code access to a private source repository should not be able to reuse or associate Git LFS objects owned by that repository. However, because the source-object accessibility check accepts broad repository access, non-Code access such as Issues access may be sufficient for the LFS object to be treated as accessible. If the reused object becomes downloadable through the attacker-controlled target repository after metadata association, this can result in cross-repository Git LFS content disclosure. The target repository write authorization is still enforced. The problem is specifically in the authorization decision for whether the source LFS object is accessible and may be reused. Preconditions The attacker needs: - an authenticated Gitea account; - Code write access to a target repository; - non-Code access, such as Issues access, to a private source repository; - knowledge of an existing Git LFS object OID and size from the private source repository. Affected Area The issue affects the Git LFS upload/object reuse path. Relevant paths: services/lfs/server.go Relevant handlers: BatchHandler UploadHandler Both paths can call: git_model.LFSObjectAccessible(ctx, ctx.Doer, p.Oid) The helper is located in: models/git/lfs.go The authorization check uses: repo_model.AccessibleRepositoryCondition(user, unit.TypeInvalid) When unit.TypeInvalid is used, the repository access