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

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-2026-7839 UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access

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 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-2026-40885

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-2026-7829 UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token

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-2026-7829

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-2026-7829

UltraVNC repeater (= destination size, the NUL byte is written past the end of the stack array, corrupting adjacent data and potentially enabling code execution on the repeater host. An attacker with admin credentials (including via CVE-2026-7839 default password) can trigger this. The provided d...

EUVD-2026-40881

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-2026-7829 UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token

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-2026-7828 UltraVNC repeater integer overflow in win_log malloc leading to heap overflow

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-2026-7828 UltraVNC repeater integer overflow in win_log malloc leading to heap overflow

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-2026-7828

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-2026-7828

UltraVNC repeater up to version 1.8.2.2 contains an integer overflow in the HTTP request logging path. In repeater/webgui/settings.c:336, win_log() allocates memory with malloc(sizeof(struct LIST) + strlen(line)); if strlen(line) is large, the size overflows to a value smaller than sizeof(struct ...

EUVD-2026-40880

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,...

EUVD-2026-40877

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-2026-44042

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-2026-44042 UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check

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-2026-44042 UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check

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...