uvnc UltraVNC up to 1.8.2.2 Setting settings.c out-of-bounds write

Summaryinfo

A vulnerability was found in uvnc UltraVNC up to 1.8.2.2. It has been classified as critical. The impacted element is an unknown function of the file repeater/webgui/settings.c of the component Setting Handler. The manipulation leads to out-of-bounds write. This vulnerability is uniquely identified as CVE-2026-7829. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in uvnc UltraVNC up to 1.8.2.2 and classified as critical. This issue affects an unknown code block of the file repeater/webgui/settings.c of the component Setting Handler. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.

The weakness was disclosed by Arjun Basnet. The identification of this vulnerability is CVE-2026-7829 since 05/05/2026. The exploitation is known to be easy. The attack may be initiated remotely. Additional levels of successful authentication are required for exploitation. 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).

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

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Productinfo

Type

• Connectivity Software

Vendor

• uvnc

Name

• UltraVNC

Version

• 1.8.2.0
• 1.8.2.1
• 1.8.2.2

License

• open-source

CPE 2.3info

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CPE 2.2info

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