CVE-2026-7830

UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme rfbUltraVNCMsLogonIIAuth. In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer DHMAXBITS controls the prime size. A 64-bit DH key can be brok...

CVE-2026-7838

UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in the RFB protocol failure-response parsing path. In vncviewer/ClientConnection.cpp, the 4-byte network-supplied reasonLen field type CARD32 is passed as reasonLen+1 to CheckBufferSize. Because both...

CVE-2026-7840

UltraVNC repeater through 1.8.2.2 contains a global buffer overflow in its embedded HTTP administration server. The functions wisenderr and wireplyhdr in repeater/webgui/webutils.c write the caller-supplied HTTP request URI into a fixed 1000-byte global buffer hdrbuf via unchecked sprintf calls...

CVE-2026-7831

UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer dn2024 and calls ReadStringdn, 2024. ReadString...

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 strncpys copies a rule token into temp1rule1 25-byte destination or temp2/temp3 16-byte destination, the code unconditionally writes a N...

CVE-2026-7839

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 strcpyssavedpassword, 64,...

CVE-2026-7828

UltraVNC repeater through 1.8.2.2 contains an integer overflow in the HTTP request logging path. In repeater/webgui/settings.c:336, the winlog function allocates list nodes via mallocsizeofstruct LIST + strlenline, where line is derived from HTTP request URIs. If strlenline is sufficiently large,...

CVE-2026-44042

UltraVNC repeater through 1.8.2.2 contains an off-by-one error in the Base64 decode helper used for HTTP Basic authentication. In repeater/webgui/webutils.c:817, the wiuudecode function checks whether the input length exceeds the output buffer with a strict greater-than comparison , while the...

CVE-2026-44041

UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb function passes a caller-supplied WCHAR pointer to wcslen before any bounds check. If the caller provides a wide-character buffer that is not properly...

CVE-2026-44040

UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes function seeds libc rand with time0 + getpid + rand and generates a 16-byte challenge. The combined seed space is...

CVE-2026-7840 UltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE)

UltraVNC repeater through 1.8.2.2 contains a global buffer overflow in its embedded HTTP administration server. The functions wisenderr and wireplyhdr in repeater/webgui/webutils.c write the caller-supplied HTTP request URI into a fixed 1000-byte global buffer hdrbuf via unchecked sprintf calls...

CVE-2026-7840

UltraVNC repeater through 1.8.2.2 contains a global buffer overflow in its embedded HTTP administration server. The functions wisenderr and wireplyhdr in repeater/webgui/webutils.c write the caller-supplied HTTP request URI into a fixed 1000-byte global buffer hdrbuf via unchecked sprintf calls...

EUVD-2026-40886

UltraVNC repeater through 1.8.2.2 contains a global buffer overflow in its embedded HTTP administration server. The functions wisenderr and wireplyhdr in repeater/webgui/webutils.c write the caller-supplied HTTP request URI into a fixed 1000-byte global buffer hdrbuf via unchecked sprintf calls...

CVE-2026-7840

CVE-2026-7840 (UltraVNC repeater) : A global buffer overflow in the embedded HTTP administration server affects UltraVNC repeater versions up to 1.8.2.2. The functions wi_senderr() and wi_replyhdr() copy the caller-supplied HTTP request URI into a fixed 1000-byte buffer (hdrbuf) using unchecked s...

CVE-2026-7840 UltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE)

UltraVNC repeater through 1.8.2.2 contains a global buffer overflow in its embedded HTTP administration server. The functions wisenderr and wireplyhdr in repeater/webgui/webutils.c write the caller-supplied HTTP request URI into a fixed 1000-byte global buffer hdrbuf via unchecked sprintf calls...

EUVD-2026-40885

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 strcpyssavedpassword, 64,...

CVE-2026-7839

UltraVNC repeater up to version 1.8.2.2 contains a hardcoded default admin password that is written during first run when settings2.txt is absent. Specifically, repeater/webgui/settings.c assigns the literal string "adminadmi2" to saved_password (64 bytes) and the HTTP Basic-auth handler wi_decod...

EUVD-2026-40884

UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in the RFB protocol failure-response parsing path. In vncviewer/ClientConnection.cpp, the 4-byte network-supplied reasonLen field type CARD32 is passed as reasonLen+1 to CheckBufferSize. Because both...

CVE-2026-7838 UltraVNC viewer heap buffer overflow via integer overflow in RFB connection-failure reason length

UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in the RFB protocol failure-response parsing path. In vncviewer/ClientConnection.cpp, the 4-byte network-supplied reasonLen field type CARD32 is passed as reasonLen+1 to CheckBufferSize. Because both...

CVE-2026-7831 UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing

UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer dn2024 and calls ReadStringdn, 2024. ReadString...