CVE-2025-34254: CWE-204 Observable Response Discrepancy in D-Link Nuclias Connect
D-Link Nuclias Connect firmware versions <= 1.3.1.4 contain an observable response discrepancy vulnerability. The application's 'Login' endpoint returns distinct JSON responses depending on whether the supplied username is associated with an existing account. Because the responses differ in the `error.message`string value, an unauthenticated remote attacker can enumerate valid usernames/accounts on the server. NOTE: D-Link states that a fix is under development.
AI Analysis
Technical Summary
CVE-2025-34254 is an observable response discrepancy vulnerability (CWE-204) in D-Link Nuclias Connect firmware versions up to 1.3.1.4. The login endpoint returns distinct JSON responses based on the validity of the supplied username, enabling unauthenticated attackers to enumerate valid accounts remotely. This information disclosure flaw does not require authentication or user interaction and has a medium severity rating with a CVSS 4.0 score of 6.9. No known exploits are reported in the wild. D-Link has stated that a fix is under development but has not yet released a patch.
Potential Impact
An unauthenticated remote attacker can determine valid usernames on the affected D-Link Nuclias Connect devices by analyzing the differing error messages returned from the login endpoint. This can facilitate further targeted attacks such as brute force or credential stuffing. There is no indication of direct system compromise or data breach from this vulnerability alone.
Mitigation Recommendations
D-Link has confirmed that a fix is under development. Until a patch is released, users should monitor official D-Link advisories for updates. No official workaround or temporary fix is currently provided. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
CVE-2025-34254: CWE-204 Observable Response Discrepancy in D-Link Nuclias Connect
Description
D-Link Nuclias Connect firmware versions <= 1.3.1.4 contain an observable response discrepancy vulnerability. The application's 'Login' endpoint returns distinct JSON responses depending on whether the supplied username is associated with an existing account. Because the responses differ in the `error.message`string value, an unauthenticated remote attacker can enumerate valid usernames/accounts on the server. NOTE: D-Link states that a fix is under development.
CVSS v4.0
Score 6.9medium
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2025-34254 is an observable response discrepancy vulnerability (CWE-204) in D-Link Nuclias Connect firmware versions up to 1.3.1.4. The login endpoint returns distinct JSON responses based on the validity of the supplied username, enabling unauthenticated attackers to enumerate valid accounts remotely. This information disclosure flaw does not require authentication or user interaction and has a medium severity rating with a CVSS 4.0 score of 6.9. No known exploits are reported in the wild. D-Link has stated that a fix is under development but has not yet released a patch.
Potential Impact
An unauthenticated remote attacker can determine valid usernames on the affected D-Link Nuclias Connect devices by analyzing the differing error messages returned from the login endpoint. This can facilitate further targeted attacks such as brute force or credential stuffing. There is no indication of direct system compromise or data breach from this vulnerability alone.
Mitigation Recommendations
D-Link has confirmed that a fix is under development. Until a patch is released, users should monitor official D-Link advisories for updates. No official workaround or temporary fix is currently provided. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Data Version
- 5.1
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2025-04-15T19:15:22.578Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 68f140779f8a5dbaeaf6e5b6
Added to database: 10/16/2025, 18:59:03 UTC
Last enriched: 05/28/2026, 20:34:44 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 355
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