Vulnerability-Lookup

CVE-2026-55678 (GCVE-0-2026-55678)

Vulnerability from cvelistv5 – Published: 2026-08-28 20:32 – Updated: 2026-09-01 01:57

Title

Arc: Unauthenticated cluster node admission when `cluster.shared_secret` is unset

Summary

Arc is an open, SQL-native time-series database for telemetry. From 26.02.1 until 26.06.2, Arc Enterprise clustering accepts cluster join requests without authentication when cluster.enabled is true but cluster.shared_secret is not configured. The defaults in internal/config/config.go set cluster.enabled to false, cluster.cluster_name to arc-cluster, cluster.coordinator_addr to :9100, cluster.shared_secret to an empty value, and cluster.tls_enabled to false, while cmd/arc/main.go requires cluster.shared_secret only when cluster.replication_enabled is true. JoinRequest in internal/cluster/protocol/messages.go accepts attacker-controlled node_id, role, raft_addr, api_addr, and coord_addr values, plus optional auth_nonce, auth_timestamp, and auth_hmac fields. The join path in internal/cluster/coordinator.go validates HMAC authentication only when the configured shared secret is non-empty and otherwise proceeds after only the cluster-name check. An accepted node is marked healthy, added as a Raft voter or registered locally, and becomes available through internal/cluster/registry.go to the routing logic in internal/cluster/router.go. The forwardRequest path in internal/cluster/router.go builds its target from node.APIAddress and copies Authorization and x-api-key headers with the request, so a rogue node selected for a forwarded query or write can receive authentication headers, request bodies, database and measurement names, and operational metadata. Heartbeat in internal/cluster/protocol/messages.go also lacks HMAC fields, and internal/cluster/coordinator.go updates node state from supplied node_id and state values without authentication. An unauthenticated network attacker who can reach the coordinator port and knows the cluster name can therefore become a trusted cluster node, mutate cluster membership, be submitted as a Raft voter, intercept topology-dependent forwarded requests, divert or forge operations, and blackhole or delay traffic. The default standalone configuration is not reachable because cluster.enabled is false, but Enterprise cluster deployments with clustering enabled and no shared secret are affected. This issue is fixed in version 26.06.2.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-01 01:57 UTC

CWE

CWE-284 - Improper Access Control
CWE-287 - Improper Authentication
CWE-306 - Missing Authentication for Critical Function

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/Basekick-Labs/arc/security/adv…	x_refsource_CONFIRM
https://github.com/Basekick-Labs/arc/pull/505	x_refsource_MISC
https://github.com/Basekick-Labs/arc/commit/38402…	x_refsource_MISC
https://github.com/Basekick-Labs/arc/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
Basekick-Labs	arc	Affected: >= 26.02.1, < 26.06.2	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55678

Vulnerability from fkie_nvd - Published: 2026-08-28 22:16 - Updated: 2026-09-01 02:16

Severity

6.9 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/Basekick-Labs/arc/commit/38402ad2ebddd32c15bf4a0fc9c22c920e5685df
	security-advisories@github.com	https://github.com/Basekick-Labs/arc/pull/505
	security-advisories@github.com	https://github.com/Basekick-Labs/arc/releases/tag/v26.06.2
	security-advisories@github.com	https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "arc",
          "vendor": "Basekick-Labs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 26.02.1, \u003c 26.06.2"
            }
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        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
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      "lang": "en",
      "value": "Arc is an open, SQL-native time-series database for telemetry. From 26.02.1 until 26.06.2, Arc Enterprise clustering accepts cluster join requests without authentication when cluster.enabled is true but cluster.shared_secret is not configured. The defaults in internal/config/config.go set cluster.enabled to false, cluster.cluster_name to arc-cluster, cluster.coordinator_addr to :9100, cluster.shared_secret to an empty value, and cluster.tls_enabled to false, while cmd/arc/main.go requires cluster.shared_secret only when cluster.replication_enabled is true. JoinRequest in internal/cluster/protocol/messages.go accepts attacker-controlled node_id, role, raft_addr, api_addr, and coord_addr values, plus optional auth_nonce, auth_timestamp, and auth_hmac fields. The join path in internal/cluster/coordinator.go validates HMAC authentication only when the configured shared secret is non-empty and otherwise proceeds after only the cluster-name check. An accepted node is marked healthy, added as a Raft voter or registered locally, and becomes available through internal/cluster/registry.go to the routing logic in internal/cluster/router.go. The forwardRequest path in internal/cluster/router.go builds its target from node.APIAddress and copies Authorization and x-api-key headers with the request, so a rogue node selected for a forwarded query or write can receive authentication headers, request bodies, database and measurement names, and operational metadata. Heartbeat in internal/cluster/protocol/messages.go also lacks HMAC fields, and internal/cluster/coordinator.go updates node state from supplied node_id and state values without authentication. An unauthenticated network attacker who can reach the coordinator port and knows the cluster name can therefore become a trusted cluster node, mutate cluster membership, be submitted as a Raft voter, intercept topology-dependent forwarded requests, divert or forge operations, and blackhole or delay traffic. The default standalone configuration is not reachable because cluster.enabled is false, but Enterprise cluster deployments with clustering enabled and no shared secret are affected. This issue is fixed in version 26.06.2."
    }
  ],
  "id": "CVE-2026-55678",
  "lastModified": "2026-09-01T02:16:58.753",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55678",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-01T01:57:11.131032Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-28T22:16:51.400",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Basekick-Labs/arc/commit/38402ad2ebddd32c15bf4a0fc9c22c920e5685df"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Basekick-Labs/arc/pull/505"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Basekick-Labs/arc/releases/tag/v26.06.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-284"
        },
        {
          "lang": "en",
          "value": "CWE-287"
        },
        {
          "lang": "en",
          "value": "CWE-306"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-P378-JP5R-GPGW

Vulnerability from github – Published: 2026-08-28 20:32 – Updated: 2026-08-28 20:32

Summary

arc has unauthenticated cluster node admission when `cluster.shared_secret` is unset

Details

Summary

Arc Enterprise clustering accepts cluster join requests without authentication when cluster.enabled=true but cluster.shared_secret is not configured. The coordinator validates HMAC authentication only if a shared secret is non-empty; otherwise, a network attacker who can reach the coordinator port can send a join request with attacker-controlled node addresses and role. Accepted nodes are marked healthy, registered locally or added as Raft voters, and can be selected by the cluster router for forwarded authenticated requests.

Details

Cluster defaults include an empty shared secret and TLS disabled:

internal/config/config.go:943-950 defaults cluster.enabled=false, cluster.cluster_name="arc-cluster", and cluster.coordinator_addr=":9100".
internal/config/config.go:1001-1005 defaults cluster.shared_secret="" and cluster.tls_enabled=false.

Startup requires a shared secret only for file replication, not for all clustering/join/routing use:

cmd/arc/main.go:1258-1265 hard-fails without cluster.shared_secret only when cluster.replication_enabled is true.

The join request contains attacker-supplied node identity, role, and addresses:

internal/cluster/protocol/messages.go:127-142 defines JoinRequest fields including node_id, role, raft_addr, api_addr, coord_addr, plus optional auth fields.

The coordinator validates HMAC only when the configured shared secret is non-empty:

internal/cluster/coordinator.go:1066-1081 wraps all HMAC checks in if c.cfg.SharedSecret != "" { ... }.
If the secret is empty, the join request proceeds after only the cluster-name check.

An accepted join creates a healthy node from attacker-controlled fields and adds it to cluster trust state:

internal/cluster/coordinator.go:1101-1107 creates a node from request fields, sets attacker-provided coordinator/API addresses, and marks it healthy.
internal/cluster/coordinator.go:1108-1129 adds the attacker-provided raft_addr as a Raft voter and stores node info when Raft is configured.
internal/cluster/coordinator.go:1133-1138 registers the node locally when Raft is not configured.

The router uses healthy nodes from this registry and forwards authenticated requests to their advertised API addresses:

internal/cluster/registry.go:263-270 returns healthy writers/readers.
internal/cluster/router.go:154-177 routes writes to healthy writer nodes.
internal/cluster/router.go:203-227 routes queries to healthy readers, or writers if no readers exist.
internal/cluster/router.go:327-357 builds the forwarding target from node.APIAddress and copies all original request headers to the peer, including Authorization and x-api-key.
cmd/arc/main.go:1887-1897 wires the cluster router into MessagePack, line protocol, TLE, and query handlers when the cluster coordinator exists.

A related lower-severity issue is that heartbeat messages are also unauthenticated:

internal/cluster/protocol/messages.go:175-180 defines Heartbeat without HMAC fields.
internal/cluster/coordinator.go:1220-1232 records heartbeats and updates node state based only on supplied node_id and state.

Proof of concept

Safe local lab reproduction only; do not target external infrastructure.

Prerequisites:

Enterprise clustering enabled in a lab deployment.
cluster.shared_secret intentionally left empty.
Network access to the coordinator TCP port, default 9100.
The attacker knows or guesses the cluster name; default is arc-cluster.

Steps:

Start an Arc cluster node with:

[cluster]
enabled = true
cluster_name = "arc-cluster"
coordinator_addr = ":9100"
shared_secret = ""
tls_enabled = false

Start an attacker-controlled HTTP listener that records request method, path, and headers, for example on 127.0.0.1:18080.
Send a framed cluster join request to the victim coordinator. The protocol uses a 4-byte big-endian length prefix, followed by a 1-byte message type (MsgJoinRequest == 1), followed by JSON. The payload should include attacker-controlled node fields and omit auth_nonce, auth_timestamp, and auth_hmac:

{
  "node_id": "evil-reader-1",
  "node_name": "evil-reader",
  "role": "reader",
  "cluster_name": "arc-cluster",
  "raft_addr": "127.0.0.1:19020",
  "api_addr": "127.0.0.1:18080",
  "coord_addr": "127.0.0.1:19010",
  "version": "lab",
  "core_count": 1
}

Expected vulnerable result: the coordinator accepts the join instead of rejecting it for missing authentication.

Trigger a forwarded operation from a node that cannot handle the operation locally. Examples depend on cluster roles:
Join as reader and trigger a query through a node that routes queries to readers.
Join as writer and trigger ingestion through a non-writer node that routes writes to writers.

Expected vulnerable result: the attacker-controlled HTTP listener receives forwarded requests. Because forwardRequest copies all original headers, the listener can observe authentication headers such as bearer tokens or API keys along with request paths and bodies.

In a Raft-enabled lab, observe that the attacker-provided raft_addr is submitted to AddVoter, demonstrating unauthorized membership mutation.

Impact

In affected cluster deployments, an unauthenticated network attacker can become a trusted cluster node. Practical impacts include:

Interception of forwarded authenticated HTTP requests, including Authorization and x-api-key headers.
Exposure of query bodies, ingestion data, database/measurement names, and operational metadata.
Unauthorized cluster membership mutation, including attempted Raft voter addition when Raft is configured.
Potential data integrity impact if the rogue node returns forged query/write responses or accepts/diverts writes.
Potential availability impact by blackholing or delaying forwarded operations.

This is not reachable in the default standalone configuration because cluster.enabled=false, but it is a critical trust-boundary issue for Enterprise cluster deployments where clustering is enabled without a shared secret. The code already treats cluster.shared_secret as mandatory for replication, which suggests unauthenticated cluster membership should also fail closed.

Suggested fix

Fail startup when cluster.enabled=true and cluster.shared_secret is empty, not only when cluster.replication_enabled=true.
Reject all trust-mutating coordinator messages when no cluster authentication is configured, including join, heartbeat/state update, forward apply, and file replication messages.
Require HMAC or mutual TLS before processing any join/heartbeat message.
Bind authentication to node identity and advertised addresses to reduce replay and address-substitution risks.
Do not forward end-user Authorization/x-api-key headers to a peer unless the peer identity has been authenticated and authorized.
Add tests proving unauthenticated join and heartbeat requests fail when clustering is enabled.

References / evidence

internal/config/config.go:943-950
internal/config/config.go:1001-1005
cmd/arc/main.go:1258-1265
internal/cluster/protocol/messages.go:127-142
internal/cluster/coordinator.go:1066-1081
internal/cluster/coordinator.go:1101-1138
internal/cluster/router.go:154-177
internal/cluster/router.go:203-227
internal/cluster/router.go:327-357
cmd/arc/main.go:1887-1897

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/basekick-labs/arc"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.0-20260615160325-38402ad2ebdd"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55678"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-284",
      "CWE-287",
      "CWE-306"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-28T20:32:57Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nArc Enterprise clustering accepts cluster join requests without authentication when `cluster.enabled=true` but `cluster.shared_secret` is not configured. The coordinator validates HMAC authentication only if a shared secret is non-empty; otherwise, a network attacker who can reach the coordinator port can send a join request with attacker-controlled node addresses and role. Accepted nodes are marked healthy, registered locally or added as Raft voters, and can be selected by the \ncluster router for forwarded authenticated requests.\n\n## Details\n\nCluster defaults include an empty shared secret and TLS disabled:\n\n- `internal/config/config.go:943-950` defaults `cluster.enabled=false`, `cluster.cluster_name=\"arc-cluster\"`, and `cluster.coordinator_addr=\":9100\"`.\n- `internal/config/config.go:1001-1005` defaults `cluster.shared_secret=\"\"` and `cluster.tls_enabled=false`.\n\nStartup requires a shared secret only for file replication, not for all clustering/join/routing use:\n\n- `cmd/arc/main.go:1258-1265` hard-fails without `cluster.shared_secret` only when `cluster.replication_enabled` is true.\n\nThe join request contains attacker-supplied node identity, role, and addresses:\n\n- `internal/cluster/protocol/messages.go:127-142` defines `JoinRequest` fields including `node_id`, `role`, `raft_addr`, `api_addr`, `coord_addr`, plus optional auth fields.\n\nThe coordinator validates HMAC only when the configured shared secret is non-empty:\n\n- `internal/cluster/coordinator.go:1066-1081` wraps all HMAC checks in `if c.cfg.SharedSecret != \"\" { ... }`.\n- If the secret is empty, the join request proceeds after only the cluster-name check.\n\nAn accepted join creates a healthy node from attacker-controlled fields and adds it to cluster trust state:\n\n- `internal/cluster/coordinator.go:1101-1107` creates a node from request fields, sets attacker-provided coordinator/API addresses, and marks it healthy.\n- `internal/cluster/coordinator.go:1108-1129` adds the attacker-provided `raft_addr` as a Raft voter and stores node info when Raft is configured.\n- `internal/cluster/coordinator.go:1133-1138` registers the node locally when Raft is not configured.\n\nThe router uses healthy nodes from this registry and forwards authenticated requests to their advertised API addresses:\n\n- `internal/cluster/registry.go:263-270` returns healthy writers/readers.\n- `internal/cluster/router.go:154-177` routes writes to healthy writer nodes.\n- `internal/cluster/router.go:203-227` routes queries to healthy readers, or writers if no readers exist.\n- `internal/cluster/router.go:327-357` builds the forwarding target from `node.APIAddress` and copies all original request headers to the peer, including `Authorization` and `x-api-key`.\n- `cmd/arc/main.go:1887-1897` wires the cluster router into MessagePack, line protocol, TLE, and query handlers when the cluster coordinator exists.\n\nA related lower-severity issue is that heartbeat messages are also unauthenticated:\n\n- `internal/cluster/protocol/messages.go:175-180` defines `Heartbeat` without HMAC fields.\n- `internal/cluster/coordinator.go:1220-1232` records heartbeats and updates node state based only on supplied `node_id` and `state`.\n\n## Proof of concept\n\nSafe local lab reproduction only; do not target external infrastructure.\n\nPrerequisites:\n\n- Enterprise clustering enabled in a lab deployment.\n- `cluster.shared_secret` intentionally left empty.\n- Network access to the coordinator TCP port, default `9100`.\n- The attacker knows or guesses the cluster name; default is `arc-cluster`.\n\nSteps:\n\n1. Start an Arc cluster node with:\n\n```toml\n[cluster]\nenabled = true\ncluster_name = \"arc-cluster\"\ncoordinator_addr = \":9100\"\nshared_secret = \"\"\ntls_enabled = false\n```\n\n2. Start an attacker-controlled HTTP listener that records request method, path, and headers, for example on `127.0.0.1:18080`.\n\n3. Send a framed cluster join request to the victim coordinator. The protocol uses a 4-byte big-endian length prefix, followed by a 1-byte message type (`MsgJoinRequest == 1`), followed by JSON. The payload should include attacker-controlled node fields and omit `auth_nonce`, `auth_timestamp`, and `auth_hmac`:\n\n```json\n{\n  \"node_id\": \"evil-reader-1\",\n  \"node_name\": \"evil-reader\",\n  \"role\": \"reader\",\n  \"cluster_name\": \"arc-cluster\",\n  \"raft_addr\": \"127.0.0.1:19020\",\n  \"api_addr\": \"127.0.0.1:18080\",\n  \"coord_addr\": \"127.0.0.1:19010\",\n  \"version\": \"lab\",\n  \"core_count\": 1\n}\n```\n\nExpected vulnerable result: the coordinator accepts the join instead of rejecting it for missing authentication.\n\n4. Trigger a forwarded operation from a node that cannot handle the operation locally. Examples depend on cluster roles:\n\n- Join as `reader` and trigger a query through a node that routes queries to readers.\n- Join as `writer` and trigger ingestion through a non-writer node that routes writes to writers.\n\nExpected vulnerable result: the attacker-controlled HTTP listener receives forwarded requests. Because `forwardRequest` copies all original headers, the listener can observe authentication headers such as bearer tokens or API keys along with request paths and bodies.\n\n5. In a Raft-enabled lab, observe that the attacker-provided `raft_addr` is submitted to `AddVoter`, demonstrating unauthorized membership mutation.\n\n## Impact\n\nIn affected cluster deployments, an unauthenticated network attacker can become a trusted cluster node. Practical impacts include:\n\n- Interception of forwarded authenticated HTTP requests, including `Authorization` and `x-api-key` headers.\n- Exposure of query bodies, ingestion data, database/measurement names, and operational metadata.\n- Unauthorized cluster membership mutation, including attempted Raft voter addition when Raft is configured.\n- Potential data integrity impact if the rogue node returns forged query/write responses or accepts/diverts writes.\n- Potential availability impact by blackholing or delaying forwarded operations.\n\nThis is not reachable in the default standalone configuration because `cluster.enabled=false`, but it is a critical trust-boundary issue for Enterprise cluster deployments where clustering is enabled without a shared secret. The code already treats `cluster.shared_secret` as mandatory for replication, which suggests unauthenticated cluster membership should also fail closed.\n\n\n## Suggested fix\n\n- Fail startup when `cluster.enabled=true` and `cluster.shared_secret` is empty, not only when `cluster.replication_enabled=true`.\n- Reject all trust-mutating coordinator messages when no cluster authentication is configured, including join, heartbeat/state update, forward apply, and file replication messages.\n- Require HMAC or mutual TLS before processing any join/heartbeat message.\n- Bind authentication to node identity and advertised addresses to reduce replay and address-substitution risks.\n- Do not forward end-user `Authorization`/`x-api-key` headers to a peer unless the peer identity has been authenticated and authorized.\n- Add tests proving unauthenticated join and heartbeat requests fail when clustering is enabled.\n\n## References / evidence\n\n- `internal/config/config.go:943-950`\n- `internal/config/config.go:1001-1005`\n- `cmd/arc/main.go:1258-1265`\n- `internal/cluster/protocol/messages.go:127-142`\n- `internal/cluster/coordinator.go:1066-1081`\n- `internal/cluster/coordinator.go:1101-1138`\n- `internal/cluster/router.go:154-177`\n- `internal/cluster/router.go:203-227`\n- `internal/cluster/router.go:327-357`\n- `cmd/arc/main.go:1887-1897`",
  "id": "GHSA-p378-jp5r-gpgw",
  "modified": "2026-08-28T20:32:57Z",
  "published": "2026-08-28T20:32:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Basekick-Labs/arc/pull/505"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Basekick-Labs/arc/commit/38402ad2ebddd32c15bf4a0fc9c22c920e5685df"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Basekick-Labs/arc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Basekick-Labs/arc/releases/tag/v26.06.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "arc has unauthenticated cluster node admission when `cluster.shared_secret` is unset"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-55678 (GCVE-0-2026-55678)

FKIE_CVE-2026-55678

GHSA-P378-JP5R-GPGW

Summary

Details

Proof of concept

Impact

Suggested fix

References / evidence

Tags

Sightings

Nomenclature