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Arcane Vulnerable to Unauthenticated Disclosure of Custom Compose Template Content (incl. `.env` secrets)

High severity GitHub Reviewed Published Apr 23, 2026 in getarcaneapp/arcane • Updated Apr 30, 2026

Package

github.com/getarcaneapp/arcane/backend (Go)

Affected versions

< 1.18.0

Patched versions

1.18.0

Description

Summary

Four GET endpoints under /api/templates* in Arcane's Huma backend are registered without any Security requirement, allowing any unauthenticated network client to list and read the full Compose YAML and .env content of every custom template stored in the instance. Because Arcane's UI exposes a "Save as Template" flow on the project / swarm-stack creation pages that persists the operator's real env content (database passwords, API keys, etc.) verbatim, this missing authorization is an unauthenticated read of operator secrets in practice — not a theoretical info-disclosure.

The frontend explicitly treats /customize/templates/* as an authenticated area (PROTECTED_PREFIXES in frontend/src/lib/utils/redirect.util.ts), and every CRUD operation (POST/PUT/DELETE) on the same paths requires a Bearer/API key, so this is a clear backend authorization gap, not intended public access.

Details

Affected file: backend/internal/huma/handlers/templates.go:194-228.

In RegisterTemplates, four huma.Register calls have no Security: block:

// templates.go
huma.Register(api, huma.Operation{
    OperationID: "listTemplatesPaginated",
    Method:      "GET",
    Path:        "/templates",
    ...
    // <-- no Security
}, h.ListTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getAllTemplates",
    Method:      "GET",
    Path:        "/templates/all",
    ...
}, h.GetAllTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getTemplate",
    Method:      "GET",
    Path:        "/templates/{id}",
    ...
}, h.GetTemplate)

huma.Register(api, huma.Operation{
    OperationID: "getTemplateContent",
    Method:      "GET",
    Path:        "/templates/{id}/content",
    ...
}, h.GetTemplateContent)

Arcane's auth bridge (backend/internal/huma/middleware/auth.go:168-172) only enforces authentication when the operation declares one of the security schemes (BearerAuth or ApiKeyAuth). With Security omitted, parseSecurityRequirements returns isRequired=false and the request flows through with no token check.

TemplateHandler.GetTemplateContent (templates.go:478-499) calls templateService.GetTemplateContentWithParsedData (backend/internal/services/template_service.go:1303-1347), which returns the model's Content, EnvContent, parsed services, and parsed env-variable key/value pairs verbatim. The model models.ComposeTemplate (backend/internal/models/template.go:15-16) stores Content and EnvContent as plain text columns and has no owner / user binding.

Impact

  • Pre-auth confidentiality breach. An unauthenticated client on the same network (or through any path-unaware reverse proxy) recovers the full envContent of every locally-stored Compose template. Because the supported "Save as Template" workflow takes the operator's real env values verbatim, this commonly includes database passwords, registry tokens, third-party API keys (Stripe, Sentry, etc.), and OIDC client secrets.
  • Internal asset enumeration. GET /api/templates returns names, descriptions, tags, and registry metadata for every template, leaking what services the team runs internally and which compose files they reuse

References

@kmendell kmendell published to getarcaneapp/arcane Apr 23, 2026
Published to the GitHub Advisory Database Apr 30, 2026
Reviewed Apr 30, 2026
Last updated Apr 30, 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 None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
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:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Missing Authorization

The product does not perform an authorization check when an actor attempts to access a resource or perform an action. Learn more on MITRE.

CVE ID

CVE-2026-42461

GHSA ID

GHSA-cxx3-hr75-4q96

Source code

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