CVE-2026-128321

Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting...

CVE-2026-128321 Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow vulnerability

Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting...

EUVD-2026-124808

Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting...

CVE-2026-128321

The TightVNC and UltraVNC viewers are susceptible to a heap-based buffer overflow within the Tight JPEG decoding component. The vulnerability exists because the software fails to validate an attacker-controlled framebuffer rectangle width against a fixed-size decoding buffer. A malicious VNC serv...

TightVNC and UltraVNC Viewer contains a heap-based buffer overflow

Overview A heap-based buffer overflow exists in the Tight JPEG decoding component of the TightVNC Windows Viewer version 1.3.10 and affected UltraVNC Windows Viewers. An attacker controlling a malicious VNC server can trigger memory corruption by sending a specially crafted screen update...

PT-2026-146110

Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting...

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-2026-7838

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-2026-7829

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-2026-7830

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-2026-7828

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...

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

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...

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...