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CVE-2026-89026 – Unauthenticated RCE via Hard-Coded JWT Key – Issabel Framework (prior to commit b97

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Summary

CVE-2026-89026 is a critical vulnerability in the Issabel Framework, the web administration layer used by Issabel PBX deployments. The framework’s pbxapi component ships with a hard-coded HS256 JWT signing key that is identical across all installations, allowing an unauthenticated remote attacker to forge valid bearer tokens and ultimately execute arbitrary operating system commands on the underlying server. The issue is rated critical severity and has reportedly been exploited in the wild.

Technical details

  • Root cause: The pbxapi/index.php file contains a static, hard-coded HS256 key used to sign and verify JWT bearer tokens (CWE-321: Use of Hard-coded Cryptographic Key). Because the key is the same in every deployment, anyone who knows it can mint a token that the application will accept as authentic.
  • Trigger conditions: An attacker crafts a JWT using the known hard-coded key and presents it as a bearer token to the pbxapi manager originate endpoint, invoking Asterisk’s System application parameter.
  • Attack vector: Network-based and unauthenticated — no valid credentials, prior session, or user interaction are required.
  • Impact: Successful exploitation results in arbitrary OS command execution in the context of the Asterisk user, enabling full compromise of the PBX host, potential call interception/eavesdropping, credential theft, and use of the compromised system as a pivot point into the internal network.

Affected software

  • Issabel Framework — all versions/commits prior to the fix commit b97dbaf0b71c1c36f841e672b664afbeb02773bd.

Severity

  • CVSS v3.1: 9.8 (Critical) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • CVSS v4.0: 9.3 (Critical) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade the Issabel Framework to a version that includes commit b97dbaf0b71c1c36f841e672b664afbeb02773bd or later, which removes the hard-coded JWT signing key.
  • If patching is not immediately possible: Restrict access to the Issabel/PBX web administration interface (pbxapi) to trusted networks only, place it behind a VPN or firewall so it is not reachable from the internet, and monitor for anomalous manager/originate API calls or unexpected System application invocations in Asterisk logs.

References

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