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CVE-2026-58630 – Unauthenticated Elevation of Privilege – Azure App Service on Azure Stack Hub

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Summary

CVE-2026-58630 is a critical (CVSS 10.0) improper access control vulnerability in Microsoft Azure App Service, affecting deployments on Azure Stack Hub — Microsoft’s on-premises hybrid cloud platform used in enterprise data centers, sovereign clouds, and regulated industries. The flaw allows an unauthenticated, remote attacker to elevate privileges over the network with no user interaction required, resulting in high confidentiality and integrity impact across security boundaries. Because Azure Stack Hub is operator-managed, patching is the customer’s direct responsibility.

Technical details

  • Root cause: Improper access control (CWE-284) within the Azure App Service component allows security boundaries to be bypassed without authentication.
  • Trigger conditions: An attacker requires only network access to a reachable Azure App Service endpoint on the target Azure Stack Hub deployment; no credentials or user interaction are needed.
  • Attack vector: Network-based, unauthenticated; low attack complexity with no privileges required and no user interaction needed.
  • Impact: Successful exploitation grants the attacker elevated privileges beyond their legitimate permissions, with high impact to confidentiality (C:H) and integrity (I:H), and scope change (S:C) indicating cross-component or cross-tenant impact within the Azure Stack Hub environment. Availability is not directly impacted (A:N).

Affected software

  • Microsoft Azure App Service for Linux on Azure Stack Hub (all affected versions as designated by Microsoft; consult the MSRC advisory for specific build references)

Severity

  • CVSS v3.1 base score: 10.0 (CRITICAL)
  • Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Mitigation and recommended actions

  • Immediate: Apply the security update published by Microsoft via the Microsoft Security Response Center (MSRC) advisory for CVE-2026-58630. Azure Stack Hub operators should consult the MSRC portal for specific update guidance applicable to their installed build.
  • Network mitigation (if immediate patching is not feasible): Restrict network access to Azure App Service endpoints on Azure Stack Hub to trusted, internal networks only. Prevent direct internet exposure of Azure Stack Hub App Service endpoints through perimeter firewall or network security group (NSG) controls until the patch is applied.
  • Inventory review: Azure Stack Hub operators should audit their deployments to confirm whether App Service is installed and internet-facing, and prioritize patching for any externally reachable instances.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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1

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