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CVE-2026-72692 – Authorization Bypass (Document Decline Forgery) – OpenSign opensignserver through 2

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Summary

CVE-2026-72692 is a missing authorization vulnerability (CWE-862) in OpenSignLabs opensignserver through version 2.37.0. An unauthenticated, remote attacker can irreversibly decline any in-flight document and forge the decline attribution to an arbitrary user via the declinedoc Parse cloud function, resulting in a HIGH-severity (CVSS 7.5) integrity impact.

Technical details

  • Root cause: The declinedoc cloud function fails to verify the caller’s identity while accepting user-controlled parameters. It writes IsDeclined, DeclineReason, and a caller-supplied DeclineBy pointer without validating who is making the request.
  • Trigger conditions: An attacker submits a decline request against an accessible document without authenticating, supplying an arbitrary DeclineBy value.
  • Attack vector: Network — remotely exploitable with no privileges and no user interaction.
  • Impact: Workflow termination (a document’s signing process is irreversibly declined) and evidentiary record falsification (the decline is attributed to an arbitrary user), compromising the integrity of the signing audit record.

Affected software

  • OpenSignLabs opensignserver, all versions from 0 through 2.37.0 (2.37.0 and earlier).

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 opensignserver to a release later than 2.37.0. Subsequent releases (2.38.0, 2.39.0, 2.40.0, and 2.40.1) are available; deploy the latest available release.
  • If no patch can be applied: Restrict network exposure of the opensignserver instance and its Parse cloud functions (for example, place it behind authenticated reverse-proxy controls or IP allow-listing) so that the declinedoc endpoint is not reachable by untrusted networks, and monitor for unexpected document decline events.

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
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