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NVD / CVE Program· CNA GitHub_M

CVE-2026-55678: Arc: Unauthenticated cluster node admission when `cluster.shared_secret` is unset

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.66% (FIRST EPSS); higher than 52% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Basekick-Labs arc 26.06.2.

Low priority for now. Upgrade to Basekick-Labs arc 26.06.2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.9 · v4.0—No exploit Fix available
Published
Aug 28, 2026
Updated
Sep 9, 2026
EPSS
0.6% · 52th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
6.9
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • Basekick-Labs arc

    • >= 26.02.1, < 26.06.2affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Gogithub.com/basekick-labs/arcbefore 0.0.0-20260615160325-38402ad2ebdd0.0.0-20260615160325-38402ad2ebdd

Same product

basekick-labs: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-48050Arc: Unauthenticated access to Go debug pprof endpoints leaks runtime state and enables CPU-burn DoS
    35Monitor
  • CVE-2026-48106Arc Enterprise cluster replication accepts unauthenticated MsgReplicateSync messages, enabling cluster-wide data injection from any TLS-trusted peer
    33Monitor
  • CVE-2026-48105Arc Enterprise cluster FSM applyRegisterFile accepts arbitrary file paths without validation, enabling cluster-wide path-traversal worm primitive
    33Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-47735Aug 21, 2026 · Arc has an authenticated arbitrary local-file read via DuckDB I/O functions that bypasses RBAC table-level checks
    28Monitor
  • Later →CVE-2026-55098Oct 30, 2026 · Arc: DuckDB I/O aliases bypass database RBAC after CVE-2026-47735
    26Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Basekick-Labs arc26.06.2 · descriptionVendor (CNA)
Go:github.com/basekick-labs/arc0.0.0-20260615160325-38402ad2ebddPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

—

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2026-481057 days apartArc Enterprise cluster FSM applyRegisterFile accepts arbitrary file paths without validation, enabling cluster-wide path-traversal worm primitive
    33Monitor
  • CVE-2026-477357 days apartArc has an authenticated arbitrary local-file read via DuckDB I/O functions that bypasses RBAC table-level checks
    28Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-284 · Improper Access Control

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

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References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records