Privilege Escalation in Cap-go via SSE Stream Abort

Publication date: 2026-06-22

Last updated on: 2026-06-24

Assigner: VulnCheck

Description

Cap-go before 12.128.2 contains a privilege inversion vulnerability in GET /build/logs/:jobId that allows read-only API key holders to cancel running native builds. The endpoint registers an abort listener on the SSE stream that unconditionally invokes cancelBuildOnDisconnect() using the privileged server-side BUILDER_API_KEY when clients disconnect, bypassing the app.build_native permission check required by the explicit POST /build/cancel/:jobId endpoint. Attackers with read-only API keys can repeatedly disrupt native build operations and CI/CD workflows by opening the log stream and dropping the connection.

CVSS Scores

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Meta Information

Published

2026-06-22

Last Modified

2026-06-24

Generated

2026-07-13

AI Q&A

2026-06-23

EPSS Evaluated

2026-07-11

NVD

CVE-2026-56280

Affected Vendors & Products

Vendor	Product	Version / Range
cap-go	cap-go	12.128.2

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-862	The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Cap-go versions before 12.128.2 and involves a privilege inversion in the GET /build/logs/:jobId endpoint. It allows users with read-only API keys to cancel running native builds, which they should not be able to do. This happens because the endpoint sets up an abort listener on the SSE stream that calls cancelBuildOnDisconnect() using a privileged server-side key without checking permissions. As a result, attackers can disrupt build operations by opening the log stream and then disconnecting.

Impact Analysis

This vulnerability can allow attackers with only read-only API keys to repeatedly cancel running native builds. This can disrupt native build operations and continuous integration/continuous deployment (CI/CD) workflows, potentially causing delays, failures, or interruptions in software development and deployment processes.

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