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CVE-2026-72545 – Unauthenticated IDOR / Authorization Bypass – OpenSign through 2.37.0

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Summary

CVE-2026-72545 is an insecure direct object reference (IDOR) / authorization bypass vulnerability in OpenSignLabs OpenSign through version 2.37.0. An unauthenticated remote attacker can write to any contact record through the updatecontacttour Parse cloud function, undermining data integrity. It carries a CVSS v3.1 base score of 7.5 (High).

Technical details

  • Root cause: The updatecontacttour Parse cloud function lacks proper authentication and authorization checks (CWE-639: Authorization Bypass Through User-Controlled Key).
  • Trigger conditions: An attacker invokes the exposed cloud function referencing an arbitrary contact record identifier; no valid credentials or session are required.
  • Attack vector: Network — the function is reachable remotely over the application’s Parse backend without authentication or user interaction.
  • Impact: Unauthenticated modification/overwrite of any contact record, compromising the integrity of contact data across the system. No confidentiality or availability impact is indicated.

Affected software

  • OpenSignLabs OpenSign — all versions from 0 through and including 2.37.0.

Severity

  • CVSS v3.1 base score: 7.5 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Mitigation and recommended actions

  • Immediate: Upgrade to an OpenSign release later than 2.37.0. The latest available release at time of writing is 2.40.1.
  • If no patch can be applied immediately: Restrict network exposure of the OpenSign / Parse backend, place the application behind authenticated access controls or a reverse proxy that limits access to trusted networks, and monitor for unexpected modifications to contact records.

References

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