VulnerabilityPublished 4 May 2026Updated 8 May 2026

CVE-2026-41684: Incusd · Incus has Nil Dereferences on Restore via Malformed YAML

Affects github.com/lxc/incus/v6/cmd/incusdSource GCVE Database

Authoritative record:CVE-2026-41684· Medium 6.5

Not known to be exploited · CVSS 6.5 Medium.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Gogithub.com/lxc/incus/v6/cmd/incusd	Affected <=6.23.0	Fixed in–

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Description

### Summary ### Details It was found that backup.GetInfo() trusts the inline backup/index.yaml config when present and only falls back to parsing the legacy backup/container/backup.yaml file if result.Config == nil. As a result, an archive can carry a valid inline config that passes the initial import preflight while also carrying a malformed legacy backup/container/backup.yaml file that is reparsed later from the restored file system. ParseConfigYamlFile() accepts YAML documents with no container section, and multiple downstream consumers then dereference .Container without checking for nil. Confirmed examples in the instance restore and import flow include backup.UpdateInstanceConfig() and internalImportFromBackup(). An authenticated user with permission to import instance backups may be able to crash the Incus daemon with a crafted backup archive whose inline backup/index.yaml is valid but whose extracted legacy backup.yaml omits container. The crash occurs in the restore path after archive extraction has begun. The flow is as follows: A crafted backup archive contains a valid backup/index.yaml file together with a malformed backup/container/backup.yaml file that omits the container section. backup.GetInfo() parses backup/index.yaml successfully, so bInfo.Config is populated from the inline config. Because result.Config != nil, GetInfo() does not fall back to backup/container/backup.yaml. instances_post.go then builds the request from bInfo.Config.Container, which succeeds because the inline config is valid. Later, storage unpack extracts backup/container/backup.yaml into the instance volume as <mountPath>/backup.yaml. backend.go then calls backup.UpdateInstanceConfig(..., mountPath), which reparses <mountPath>/backup.yaml through ParseConfigYamlFile(). Because ParseConfigYamlFile() accepts YAML with no container section, backup.Container == nil, and later access to backup.Container.Devices or backup.Container.ExpandedDevices can trigger a nil-pointer dereference. Affected Files: - https://github.com/lxc/incus/blob/v6.22.0/internal/server/backup/backup_info.go#L87 - https://github.com/lxc/incus/blob/v6.22.0/internal/server/backup/backup_info.go#L115 - https://github.com/lxc/incus/blob/v6.22.0/internal/server/backup/backup_config_utils.go#L85 - https://github.com/lxc/incus/blob/v6.22.0/internal/server/backup/backup_config_utils.go#L159 - https://github.com/lxc/incus/blob/v6.22.0/internal/server/storage/backend.go#L809 - https://github.com/lxc/incus/blob/v6.22.0/cmd/incusd/api_internal.go#L749 The initial backup-metadata parser prefers inline backup/index.yaml content: Affected Code: ``` if hdr.Name == backupIndexPath { err = yaml.NewDecoder(tr).Decode(&result) ``` The legacy backup/container/backup.yaml file is only parsed if the inline config is absent: Affected Code: ``` if result.Config == nil && hdr.Name == "backup/container/backup.yaml" { err = yaml.NewDecoder(tr).Decode(&result.Config) ``` ParseConfigYamlFile() accepts an empty YAML document, or one with no container section, without validation: Affected Code: ``` func ParseConfigYamlFile(path string) (*config.Config, error) { data, err := os.ReadFile(path) ... backupConf := config.Config{} err = yaml.Unmarshal(data, &backupConf) ``` UpdateInstanceConfig() conditionally uses backup.Container at first but later dereferences it unconditionally: Affected Code: ``` if backup.Container != nil { backup.Container.Name = b.Name backup.Container.Project = b.Project } if updateRootDevicePool(backup.Container.Devices, pool.Name) { rootDiskDeviceFound = true } if updateRootDevicePool(backup.Container.ExpandedDevices, pool.Name) { rootDiskDeviceFound = true } ``` Another confirmed sink is present in internalImportFromBackup(): Affected Code: ``` if allowNameOverride { backupConf.Container.Name = instName } if instName != backupConf.Container.Name { return fmt.Errorf("Instance name requested %q doesn't match instance name in backup config %q", instName, backupConf.Container.Name) } ``` This was confirmed as follows: Command: ``` go test ./test/fuzz -run='TestExtractedBackupYAMLMissingContainerNilDereference' -count=1 -v ``` Output: ``` === RUN TestExtractedBackupYAMLMissingContainerNilDereference === RUN TestExtractedBackupYAMLMissingContainerNilDereference/legacy_backup_empty extracted_backup_yaml_poc_test.go:70: UpdateInstanceConfig panicked on malformed extracted backup.yaml (container is nil): runtime error: invalid memory address or nil pointer dereference === RUN TestExtractedBackupYAMLMissingContainerNilDereference/legacy_backup_pool_only extracted_backup_yaml_poc_test.go:70: UpdateInstanceConfig panicked on malformed extracted backup.yaml (container is nil): runtime error: invalid memory address or nil pointer dereference === RUN TestExtractedBackupYAMLMissingContainerNilDereference/legacy_backup_volume_only extracted_backup_yaml_poc_t

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-476

Technical details

References

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