← Vulnerability feed

Vulnerability record · CVE-2026-7839 · published 1 July 2026

CVE-2026-7839: Uvnc ultravnc hard-coded credentials vulnerability

Uvnc · Ultravnc

UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.

9.1 CVSS 3.1 Critical EPSS 0.66% · top 50.6% CWE-798 · Hard-coded credentials
9.1CVSS 3.1 base score
0.66%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
9 Jul 2026Last modified by NVD

Description

UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/ultravnc/UltraVNC Product
https://uvnc.com/ ProductRelease Notes
https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater

Track CVE-2026-7839 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2019-8264Uvnc ultravnc out-of-bounds read vulnerabilityUltraVNC revision 1203 has out-of-bounds access vulnerability in VNC client inside Ultra2 decoder, which can potentially result in code execution. Th…EPSS 3.1%9.8CVE-2019-8265Uvnc ultravnc out-of-bounds read vulnerabilityUltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of SETPIXELS macro in VNC client code, which c…EPSS 3.1%9.8CVE-2019-8266Uvnc ultravnc out-of-bounds read vulnerabilityUltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of ClientConnection::Copybuffer function in VN…EPSS 2.8%9.8CVE-2019-8268Uvnc ultravnc vulnerabilityUltraVNC revision 1206 has multiple off-by-one vulnerabilities in VNC client code connected with improper usage of ClientConnection::ReadString funct…EPSS 3.9%9.8CVE-2019-8271Uvnc ultravnc heap-based buffer overflow vulnerabilityUltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer handler, which can potentially result code ex…EPSS 8.3%9.8CVE-2019-8272Uvnc ultravnc vulnerabilityUltraVNC revision 1211 has multiple off-by-one vulnerabilities in VNC server code, which can potentially result in code execution. This attack appear…EPSS 3.9%9.8CVE-2019-8273Uvnc ultravnc heap-based buffer overflow vulnerabilityUltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer request handler, which can potentially result…EPSS 8.3%9.8CVE-2019-8274Uvnc ultravnc heap-based buffer overflow vulnerabilityUltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer offer handler, which can potentially in resul…EPSS 8.3%

Source: NIST National Vulnerability Database (record CVE-2026-7839), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.