CVE-2026-7829
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.
- Score
- CVSS 3.1 7.2 High
- Status
- Modified - 33c584b5-0579-4c06-b2a0-8d8329fcab9c
- Published
- 2026-07-01
- Last modified
- 2026-10-25
- Weaknesses
- CWE-787
Affected products
References
- https://uvnc.com/
- https://github.com/ultravnc/UltraVNC
- https://www.securin.io/zero-days/cve-2026-7829-post-auth-oob-nul-write-repeater-rule-parser-ultravnc
