Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message containing a subrectangle outside of the client drawing area.

Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions.

It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames. A malicious attacker could exploit this by sending specially crafted WebSocket frames to a server, causing a heap-based buffer overflow.

An issue was discovered in LibVNCServer through 0.9.11. rfbProcessClientNormalMessage() in rfbserver.c does not sanitize msg.cct.length, leading to access to uninitialized and potentially sensitive data or possibly unspecified other impact (e.g., an integer overflow) via specially crafted VNC packets.

An issue was discovered in LibVNCServer before 0.9.13. Byte-aligned data is accessed through uint32_t pointers in libvncclient/rfbproto.c. NOTE: there is reportedly "no trust boundary crossed.

An issue was discovered in LibVNCServer before 0.9.13. Byte-aligned data is accessed through uint16_t pointers in libvncserver/translate.c. NOTE: Third parties do not consider this to be a vulnerability as there is no known path of exploitation or cross of a trust boundary

An issue was discovered in LibVNCServer before 0.9.13. libvncserver/scale.c has a pixel_value integer overflow.

A divide by zero issue was found to occur in libvncserver-0.9.12. A malicious client could use this flaw to send a specially crafted message that, when processed by the VNC server, would lead to a floating point exception, resulting in a denial of service.

libvncclient v0.9.13 was discovered to contain a memory leak via the function rfbClientCleanup().

LibVNCServer versions 0.9.15 and prior (fixed in commit 009008e) contain a heap out-of-bounds read vulnerability in the UltraZip encoding handler that allows a malicious VNC server to cause information disclosure or application crash. Attackers can exploit improper bounds checking in the HandleUltraZipBPP() function by manipulating subrectangle header counts to read beyond the allocated heap buffer.

LibVNCServer versions 0.9.15 and prior (fixed in commit dc78dee) contain null pointer dereference vulnerabilities in the HTTP proxy handlers within httpProcessInput() in httpd.c that allow remote attackers to cause a denial of service by sending specially crafted HTTP requests. Attackers can exploit missing validation of strchr() return values in the CONNECT and GET proxy handling paths to trigger null pointer dereferences and crash the server when httpd and proxy features are enabled.