CVE-2026-7829 is a post-authentication out-of-bounds write vulnerability in UltraVNC repeater through version 1.8.2.2. The flaw exists in the allow/deny rule parser within repeater/webgui/settings.c, where after copying a rule token into fixed-size buffers (temp1[rule1] with 25 bytes, temp2/temp3 with 16 bytes), the code writes a NUL terminator at an index equal to the token length without verifying that the length fits within the buffer. This results in a stack buffer overflow that corrupts adjacent stack data. An attacker with administrative credentials can exploit this to achieve code execution on the repeater host.

Successful exploitation allows an attacker with administrative privileges to execute arbitrary code on the UltraVNC repeater host, potentially compromising the system's confidentiality, integrity, and availability. The vulnerability is rated with a CVSS 3.1 score of 7.2 (High), reflecting network attack vector, low attack complexity, required high privileges, no user interaction, and high impact on confidentiality, integrity, and availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict administrative access to trusted users only and monitor for unauthorized credential use. Avoid using default or weak passwords (see CVE-2026-7839) to reduce risk of credential compromise.