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.

CVSS v3 7.2 HIGH

7.2^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.2 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required HIGH

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/ultravnc/UltraVNC	Product
https://uvnc.com/	Product Release Notes
https://www.securin.io/zero-days/cve-2026-7829-post-auth-oob-nul-write-repeater-rule-parser-ultravnc

Configurations

Configuration 1 (hide)

cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*

History

09 Jul 2026, 06:16

Type	Values Removed	Values Added
References		() https://www.securin.io/zero-days/cve-2026-7829-post-auth-oob-nul-write-repeater-rule-parser-ultravnc -

02 Jul 2026, 15:09

Type	Values Removed	Values Added
CPE		cpe:2.3:a:uvnc:ultravnc::::::::
References	~~() https://github.com/ultravnc/UltraVNC -~~	() https://github.com/ultravnc/UltraVNC - Product
References	~~() https://uvnc.com/ -~~	() https://uvnc.com/ - Product, Release Notes
First Time		Uvnc Uvnc ultravnc

01 Jul 2026, 05:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-01 05:16

Updated : 2026-07-09 06:16

NVD link : CVE-2026-7829

Mitre link : CVE-2026-7829

CVE.ORG link : CVE-2026-7829

JSON object : View

Products Affected

uvnc

ultravnc

CWE

CWE-787

Out-of-bounds Write

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