Description

Improper handling of an unexpected value size in the decryption path of a client-side encryption library can cause a failed internal check that terminates the process using the library. A party able to place a suitably formed encrypted value where an application will decrypt it, or able to control the responses the application receives, may cause that application to stop running.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-09-03T15:17:36.547Z",
  "pubdate": "2026-09-03T15:17:36.547Z",
  "executiveSummary": "This vulnerability involves a Denial-of-Service (DoS) condition within a client-side encryption library caused by improper input validation during the decryption process. The vulnerability stems from the library's failure to handle unexpected ciphertext value sizes, leading to a failed internal assertion or safety check that triggers an immediate process termination.\nThe impact of this flaw is a complete application crash, rendering the service unavailable. This constitutes a significant operational risk, particularly in environments where high availability is critical. An attacker can exploit this by injecting malformed or specifically crafted encrypted payloads into any application input field or communication stream that the library processes.\nThe vulnerability does not require authentication or elevated privileges, provided the attacker can influence the data being passed to the decryption routine. By controlling either the encrypted input directly or manipulating the responses an application receives from an external source, an attacker can reliably cause the application process to terminate, effectively disrupting service availability without needing deep system access.",
  "technicalDetails": "The root cause of this vulnerability lies in the decryption path's logic, specifically during the initial stage of processing an encrypted payload. The library fails to perform robust bounds checking or validation on the size of the provided encrypted input before initiating the cryptographic transformation or parsing steps.\nIn a secure implementation, an encryption library should gracefully handle malformed input by returning an error code or an exception that the calling application can handle without terminating. However, in this implementation, the library encounters an unexpected value size that violates an internal safety assumption, triggering an unhandled exception or a hard-coded abort call. Because the library is executed within the context of the host application, this failure propagates upwards, resulting in a process-level crash.\nThe attack flow typically involves an adversary acting as a man-in-the-middle or a malicious user providing input to an application endpoint. When the application passes this payload to the vulnerable decryption function, the library attempts to process the size of the ciphertext. Upon identifying a size that is mathematically incompatible with the expected padding or structure of the encryption algorithm, the library's internal sanity check fails.\nBecause the crash occurs during the decryption lifecycle—an early stage in the data processing pipeline—the attacker does not need to bypass subsequent cryptographic security controls. The vulnerability acts as a 'crash-on-decrypt' primitive. If an attacker can force the application to decrypt multiple such inputs, they can achieve persistent service disruption or state instability.\nThis vulnerability is particularly concerning in client-side libraries where the library is often trusted to handle data from external entities without secondary validation. The lack of proper exception handling means that even if the library is used in a multi-threaded application, a single malformed payload can terminate the entire process, impacting all concurrent operations handled by that specific instance."
}