# CVE-2026-13639: Synology DiskStation Manager insufficient entropy in login logic

Source: https://junglewise.ai/threats/cve-2026-13639-synology-diskstation-manager-insufficient-entropy-in-login-logic  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-13639 · Severity: critical · CVSS 9.8 · Published 2026-09-18

Synology DiskStation Manager (DSM) is a network storage operating system that manages file access and user authentication on NAS devices. An insufficient entropy flaw in the login logic allows remote attackers without credentials to read or write arbitrary files and disrupt service availability. This exposes sensitive data and enables attackers to compromise the entire NAS device.

Technologies: [Synology DiskStation Manager](https://junglewise.ai/threats/technologies/diskstation-manager). Vendors: [Synology](https://junglewise.ai/threats/vendors/synology).

## Quick answers

**Is CVE-2026-13639 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-13639 being exploited in the wild.

**How severe is CVE-2026-13639?** Critical severity, with a CVSS score of 9.8, published 18 September 2026.

**Which products and versions are affected?** Synology DiskStation Manager before 7.2.1-69057-12, 7.2.2 before 7.2.2-72806-9, 7.3 before 7.3.2-86009-4, 7.4 before 7.4-90075.

**Is there a fix for CVE-2026-13639?** A patch was published on 2026-09-18: Multiple patch releases published across DSM version branches Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-13639 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-13639?** Check whether you run Synology DiskStation Manager at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This vulnerability is a CWE-331 (Insufficient Entropy) flaw in DSM's login logic that allows remote attackers to bypass authentication without credentials. The weak entropy in login mechanisms enables an attacker to predict or brute-force authentication tokens or session identifiers. No user interaction or authentication is required; the attack is performed remotely over the network. Successful exploitation allows attackers to achieve confidentiality, integrity, and availability impacts: reading arbitrary files, modifying stored data, and denying service. Patches are available in DSM 7.2.1-69057-12 or later, 7.2.2-72806-9 or later, 7.3.2-86009-4 or later, and 7.4-90075 or later.

## Affected products

- Synology DiskStation Manager before 7.2.1-69057-12, 7.2.2 before 7.2.2-72806-9, 7.3 before 7.3.2-86009-4, 7.4 before 7.4-90075

## Timeline

- 2026-09-18: disclosed
- 2026-09-18: patched: Multiple patch releases published across DSM version branches

## References

- [https://www.synology.com/en-global/security/advisory/Synology_SA_26_13](https://www.synology.com/en-global/security/advisory/Synology_SA_26_13)

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