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CVE-2026-72543 – Unauthenticated Contact Record Disclosure (IDOR) – OpenSign through 2.37.0

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Summary

CVE-2026-72543 is an insecure direct object reference (IDOR) / authorization bypass vulnerability in OpenSignLabs OpenSign through version 2.37.0. An unauthenticated remote attacker can retrieve contact records containing personally identifiable information without any credentials. The issue is rated HIGH severity (CVSS 7.5).

Technical details

  • Root cause: the getcontact Parse cloud function executes with useMasterKey and performs no authentication or authorization checks before returning the requested contact object (CWE-639: Authorization Bypass Through User-Controlled Key).
  • Trigger conditions: an attacker supplies a contact identifier to the vulnerable cloud function; because the function runs with master-key privileges, the object ACL is bypassed and the record is returned.
  • Attack vector: Network — remotely reachable, no privileges and no user interaction required.
  • Impact: unauthenticated enumeration and disclosure of contact records, exposing personally identifiable information (confidentiality). No integrity or availability impact.

Affected software

  • OpenSignLabs OpenSign: all versions from 0 through 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:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: monitor the official OpenSign repository for a fixed release and upgrade beyond 2.37.0 once available. At the time of writing no fixed version had been confirmed by the vendor.
  • If no patch: restrict network exposure of the OpenSign server to trusted networks, place it behind authenticated proxy/VPN access, and enforce authorization at the API gateway or reverse proxy for calls to the affected cloud function until a fix is applied.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw response body: opensign-server is running!!!
  • description meta tag content: The fastest way to sign PDFs & request signatures from others

References

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How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

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  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
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