Missing Authorization in WebSocket Master Handler Agent Parameter

A flaw has been found in will-moss Isaiah up to 1.36.9. The impacted element is the function Server.Handle of the file app/server/server/server.go of the component Master Websocket Handler. Executing a manipulation of the argument Agent can lead to missing authorization. It is possible to launch the attack remotely. The pull request to fix this issue awaits acceptance.

Casky was already ahead

This CVE exploits attack patterns that Casky's 283matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

CVE-2026-15541 is a missing authorization vulnerability in will-moss Isaiah affecting versions up to 1.36.9. The flaw exists in the Server.Handle function within the Master Websocket Handler component, where improper validation of the Agent parameter allows attackers to bypass authorization controls and manipulate websocket connections remotely. This vulnerability is particularly critical for organizations using Isaiah for agent-based infrastructure management, as it exposes the entire agent command and control channel to unauthorized access—potentially enabling lateral movement, privilege escalation, and persistent remote access without proper authentication checks.

Casky.ai's 283 mapped skills leverage Claude's extended reasoning to correlate this authorization bypass with MITRE ATT&CK techniques TA0004 (Privilege Escalation) and TA0006 (Credential Access). Practitioners using Casky would observe detection patterns highlighting: (1) unauthenticated websocket connections establishing agent sessions without proper credential validation (CWE-862: Missing Authorization), (2) insufficient authorization checks on the Agent parameter allowing unauthorized callers to assume agent identities (CWE-863: Improper Authorization), and (3) lateral movement indicators where attackers leverage the compromised handler to pivot through connected agents. The platform's skill set would flag suspicious websocket handler invocations, unauthorized agent parameter manipulation attempts, and authentication gaps in the app/server/server/server.go component, enabling defenders to identify exploitation attempts before agents are compromised.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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283 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-15541.

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

Access with Stolen Session Cookie

identity access management · low

Run

MITRE ATT&CK Techniques

TA0004 TA0006

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