CVE-2026-55678Public exploitNetwork attack vectorHinoki check available

Unauthenticated cluster admission via skipped HMAC validation

Published Aug 28, 2026 · Updated Aug 28, 2026

Improper authentication in Basekick Labs Arc 26.02.1 through 26.06.1 allows remote attackers to join Enterprise clusters as trusted nodes. The coordinator's join path skips HMAC validation when cluster.shared_secret is empty, then registers attacker-supplied identities, roles, and addresses as healthy nodes. Exploitation requires Enterprise clustering, coordinator-port access, and the cluster name; rogue nodes can alter membership and intercept or disrupt forwarded operations.

CVSS severity6.9
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Improper authentication in Basekick Labs Arc 26.02.1 through 26.06.1 allows remote attackers to join Enterprise clusters as trusted nodes. The coordinator's join path skips HMAC validation when cluster.shared_secret is empty, then registers attacker-supplied identities, roles, and addresses as healthy nodes. Exploitation requires Enterprise clustering, coordinator-port access, and the cluster name; rogue nodes can alter membership and intercept or disrupt forwarded operations.

The record

CVE
CVE-2026-55678
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Basekick Labs
Product
Arc
Classifications
CWE-284, CWE-306, CWE-287, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 26.02.1, < 26.06.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Basekick Labs · Arcversion=>= 26.02.1, < 26.06.2

Published CVSS scores

6.9GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-284Improper Access Control
CWE-306Missing Authentication for Critical Function
CWE-287Improper Authentication
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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