Description

An insufficient entropy vulnerability in login logic in Synology DiskStation Manager (DSM) before 7.2.1-69057-12, 7.2.2-72806-9, 7.3.2-86009-4 and 7.4-90075 allows remote attackers to read or write arbitrary files and conduct denial-of-service attacks.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-18T09:16:38.757Z",
  "pubdate": "2026-09-18T09:16:38.757Z",
  "executiveSummary": "This vulnerability involves an insufficient entropy issue within the login logic of Synology DiskStation Manager (DSM), categorized as an improper implementation of cryptographic randomness.\nThe flaw allows remote, unauthenticated attackers to potentially bypass security controls, leading to critical impacts including arbitrary file read and write operations and the facilitation of denial-of-service (DoS) conditions.\nAffected products include Synology DSM versions prior to 7.2.1-69057-12, 7.2.2-72806-9, 7.3.2-86009-4, and 7.4-90075.\nThe risk implication is severe, as the compromise of session generation or login tokens allows for unauthorized administrative interaction with the storage system.\nExploitation requires network access to the DSM management interface. Successful exploitation grants an attacker the capability to interact with the underlying filesystem, compromising data confidentiality and integrity, or destabilizing system availability.",
  "technicalDetails": "The root cause of this vulnerability lies in the insufficient entropy utilized by the login logic components of Synology DSM during session initialization or cryptographic token generation. In secure systems, entropy must be sourced from a cryptographically secure pseudorandom number generator (CSPRNG) to ensure that tokens are non-deterministic and unpredictable.\nWhen the entropy source is inadequate or predictable, an attacker can perform cryptanalysis on observed session artifacts or authentication sequences to calculate future or current valid session parameters. This enables the bypass of authentication mechanisms entirely, effectively spoofing authorized users or administrative sessions.\nThe attack flow commences with the attacker monitoring the login process to collect a series of cryptographic samples generated by the flawed component. By identifying patterns or biases within the output of the insufficient entropy source, the attacker can conduct an offline or online brute-force or predictive analysis to guess a valid session identifier.\nOnce the attacker successfully predicts or derives a valid session identifier, they can inject this token into their own client requests, thereby masquerading as an authenticated entity. Due to the tight integration of the login module with core system management APIs, the attacker can leverage these authenticated sessions to execute administrative commands.\nArbitrary file read and write capabilities are achieved by invoking system-level functions that fail to properly sanitize input when triggered by an attacker with an 'authenticated' session. The attacker can direct the system to read sensitive configuration files, system logs, or private data stored on the DiskStation volumes. Conversely, the write capability allows for the injection of malicious code, modification of system binaries, or overwriting of configuration files to establish persistence.\nThe denial-of-service vector is realized by utilizing the arbitrary file write capability to corrupt critical system files or by overwhelming the login service with maliciously crafted tokens that induce resource exhaustion. By targeting the integrity of the filesystem or the stability of the management daemon, the attacker can force the DSM instance into an unresponsive or crashed state, requiring administrative intervention to restore service."
}