CVE-2026-7829 Uvnc CVE debrief

Who should care

Administrators and users of UltraVNC repeater versions up to 1.8.2.2 should be aware of this vulnerability and take necessary actions to mitigate it. This includes reviewing and applying patches or upgrades, restricting access to the UltraVNC repeater to trusted administrators, and monitoring for suspicious activity. Security teams and vulnerability management teams should also be aware of this vulnerability and prioritize patching or mitigation efforts accordingly.

Technical summary

The vulnerability is caused by a post-authentication out-of-bounds write in the allow/deny rule parser. Specifically, 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. This can lead to a stack buffer overflow and potentially allow an attacker to execute arbitrary code. The vulnerability has a CVSS score of 7.2 and is classified as HIGH severity.

Defensive priority

High

Recommended defensive actions

• Apply the vendor patch or upgrade to a version beyond 1.8.2.2
• Restrict access to the UltraVNC repeater to trusted administrators
• Monitor for suspicious activity on the UltraVNC repeater
• Consider implementing additional security controls, such as multi-factor authentication
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-01T05:16:24.087Z and was last modified on 2026-07-09T06:16:21.617Z. The NVD entry is currently Modified. This information is based on the NVD entry and CVE record. The vulnerability affects UltraVNC repeater through 1.8.2.2. There may be additional details in the vendor's documentation or release notes that should be reviewed for comprehensive understanding.

Official resources