CVE-2026-75106 in OpnForm
Summary
by MITRE • 08/18/2026
OpnForm derives editable-submission secrets from sequential row identifiers using Hashids with an empty default salt, allowing unauthenticated attackers to compute hashes for any submission. Attackers can read other respondents' full submission data through the submission-fetch endpoint or overwrite submissions by supplying predicted hashes to the answer endpoint.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability in OpnForm stems from a critical flaw in its cryptographic implementation regarding the generation of secrets used to protect user-submitted forms. Specifically, the system derives editable-submission secrets based on sequential row identifiers using the Hashids library with an empty default salt. This configuration fundamentally undermines the security model because it removes the necessary randomness and unpredictability required for secure token generation. In a properly secured application, salts should be unique per instance or at least sufficiently random to prevent precomputation attacks. By utilizing an empty salt alongside sequential identifiers, which are often predictable or easily enumerated by attackers, OpnForm creates a deterministic relationship between public data structures like row IDs and private secrets used for authentication and authorization checks on submission endpoints.
This architectural weakness allows unauthenticated actors to trivially compute the correct hashes required to access sensitive information without any valid credentials. Since the input space is limited to sequential integers and the hashing algorithm with an empty salt produces consistent outputs, attackers can iterate through potential row identifiers to generate corresponding secrets. Once these predicted hashes are obtained, they can be exploited against two primary endpoints within the application. The first vector involves accessing the submission-fetch endpoint, where supplying a validly computed hash grants read access to the full content of other respondents' submissions. This results in a severe breach of confidentiality and privacy, exposing personally identifiable information or sensitive business data contained within form responses.
The second exploitation path targets the answer endpoint, enabling attackers to overwrite existing submissions with malicious payloads. By predicting the correct secret associated with a specific submission row, an attacker can manipulate the state of the application by injecting false answers or destructive content into forms that were previously submitted by legitimate users. This capability not only compromises data integrity but also undermines trust in the platform's ability to preserve user input accurately. The combination of read and write access via predicted hashes represents a critical failure in access control mechanisms, effectively bypassing authentication requirements entirely through cryptographic prediction rather than brute force or credential theft.
From an industry standard perspective, this vulnerability aligns closely with CWE-347 Improper Verification of Cryptographic Signature, as the system fails to ensure that the secret tokens are unpredictable and unique enough to prevent forgery. It also relates to CWE-285 Improper Authorization, since unauthenticated users can perform actions reserved for authorized respondents due to weak token generation practices. In terms of MITRE ATT&CK mapping, this scenario exemplifies techniques associated with T1078 Valid Accounts if the attacker leverages predicted tokens as valid credentials, and potentially T1190 Exploit Public-Facing Application by targeting a web service exposed to untrusted networks. The lack of rate limiting or anomaly detection further exacerbates the risk, allowing automated enumeration attacks to succeed without triggering defensive alerts.
To mitigate this vulnerability, immediate remediation efforts must focus on replacing the current hashing mechanism with a cryptographically secure random token generator that incorporates unique salts for each submission instance. Implementing UUIDs or similar high-entropy identifiers instead of relying solely on sequential row IDs would significantly increase the computational cost required to predict valid secrets. Additionally, integrating server-side validation checks that verify not only the presence of a hash but also its freshness and uniqueness against known active sessions can help prevent replay attacks. Enforcing strict rate limiting on submission-related endpoints will further hinder automated enumeration attempts by attackers attempting to brute-force or guess these derived values. Long-term architectural reviews should ensure that all security-critical identifiers are generated using established cryptographic standards such as those outlined in NIST guidelines for random number generation, ensuring that no predictable patterns remain exploitable by external adversaries.