uvnc UltraVNC up to 1.8.2.2 Setting settings.c wi_decode_auth hard-coded credentials

Summaryinfo

A vulnerability, which was classified as critical, has been found in uvnc UltraVNC up to 1.8.2.2. This vulnerability affects the function wi_decode_auth of the file repeater/webgui/settings.c of the component Setting Handler. This manipulation causes hard-coded credentials. This vulnerability appears as CVE-2026-7839. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability classified as critical was found in uvnc UltraVNC up to 1.8.2.2. Affected by this vulnerability is the function wi_decode_auth of the file repeater/webgui/settings.c of the component Setting Handler. The manipulation with an unknown input leads to a hard-coded credentials vulnerability. The CWE definition for the vulnerability is CWE-798. The product contains hard-coded credentials, such as a password or cryptographic key, which it uses for its own inbound authentication, outbound communication to external components, or encryption of internal data. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.

The weakness was presented by Arjun Basnet. This vulnerability is known as CVE-2026-7839 since 05/05/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/01/2026). The attack technique deployed by this issue is T1110.001 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-40885). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Connectivity Software

Vendor

• uvnc

Name

• UltraVNC

Version

• 1.8.2.0
• 1.8.2.1
• 1.8.2.2

License

• open-source

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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