uvnc UltraVNC up to 1.8.2.2 Setting settings.c win_log integer overflow

Summaryinfo

A vulnerability described as problematic has been identified in uvnc UltraVNC up to 1.8.2.2. Affected by this vulnerability is the function win_log of the file repeater/webgui/settings.c of the component Setting Handler. Executing a manipulation can lead to integer overflow. This vulnerability is registered as CVE-2026-7828. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in uvnc UltraVNC up to 1.8.2.2. It has been declared as problematic. This vulnerability affects the function win_log of the file repeater/webgui/settings.c of the component Setting Handler. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect availability. CVE summarizes:

UltraVNC repeater through 1.8.2.2 contains an integer overflow in the HTTP request logging path. In repeater/webgui/settings.c:336, the win_log() function allocates list nodes via malloc(sizeof(struct LIST) + strlen(line)), where line is derived from HTTP request URIs. If strlen(line) is sufficiently large, the addition overflows to a value smaller than sizeof(struct LIST), causing a heap allocation smaller than required. The subsequent strcpy of the full string into the undersized allocation produces a heap buffer overflow. In the current implementation this overflow is bounded by the HTTP receive buffer size (WI_RXBUFSIZE = 153600 bytes, well below SIZE_MAX on 32-bit builds), limiting practical exploitability to a partial heap write. A remote unauthenticated attacker can trigger the theoretical overflow path by sending a maximally-sized URI in an HTTP request to the repeater HTTP port.

The weakness was published by Arjun Basnet. This vulnerability was named CVE-2026-7828 since 05/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available.

Upgrading eliminates this vulnerability.

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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

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CPE 2.2info

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