GHSA-7wvc-rvp7-w99x Gitea: LFS authentication bypass via malformed SSH sub-verb allows unauthorized read access to private repositories

• Go code.gitea.io/gitea: >= 1.23.0, < 1.26.3 → fixed in 1.26.3

Summary A flaw in SSH LFS sub-verb handling allows any authenticated SSH user to obtain valid LFS credentials for any repository on the instance, including private repositories they have no access to. This enables unauthorized download of all LFS objects from any private repository. Details In `cmd/serv.go`, the `getAccessMode` function determines the required access level for SSH operations. For LFS verbs (`git-lfs-authenticate`, `git-lfs-transfer`), it switches on the sub-verb (`upload`/`download`). If the sub-verb is neither, execution falls through to: ```go setting.PanicInDevOrTesting("unknown verb: %s %s", verb, lfsVerb) return perm.AccessModeNone ``` In production (`IsProd=true`), `PanicInDevOrTesting` only logs an error and does not panic. `AccessModeNone` (value `0`) is then passed to `ServCommand` in `routers/private/serv.go`, where the permission check block at line ~322 evaluates: ```go if repoExist && (mode > perm.AccessModeRead || repo.IsPrivate || owner.Visibility.IsPrivate() || (user != nil && user.IsRestricted) || setting.Service.RequireSignInViewStrict) { ... if userMode ","size":}]}' Returns download URL with valid authorization header 4. Download private LFS content curl -H "Authorization: Bearer eyJ..." \ "https://gitea-instance/admin/private-repo.git/info/lfs/objects/" Returns the private LFS object content ``` Impact Any user with SSH access to a Gitea instance (which includes any registered user if self-registration is enabled) can read LFS objects from any private repository on the instance, regardless of their actual repository permissions. This is a confidentiality breach affecting all Gitea deployments running in production mode with SSH and LFS enabled (the default configuration). Suggested fix Validate the LFS sub-verb before calling `getAccessMode`, or return an error instead of `AccessModeNone` for unknown verbs: ```go case git.CmdVerbLfsAuthenticate, git.CmdVerbLfsTransfer: switch lfsVerb { case git.CmdSubVerbLfsUpload: return perm.AccessModeWrite case git.CmdSubVerbLfsDownload: return perm.AccessModeRead default: return fail(ctx, "Unknown LFS verb", "Unknown LFS verb: %s", lfsVerb) } ```