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.

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.

Ramin Farajpour Cami discovered that LibVNCServer incorrectly handled certain malformed unix socket names. A remote attacker could exploit this with a crafted socket name, leading to a denial of service, or possibly execute arbitrary code. (CVE-2019-20839) It was discovered that LibVNCServer did not properly access byte-aligned data. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. This issue only affected Ubuntu 18.04 LTS and Ubuntu 16.04 LTS. (CVE-2019-20840) Christian Beier discovered that LibVNCServer incorrectly handled anonymous TLS connections. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. This issue only affected Ubuntu 20.04 LTS. (CVE-2020-14396) It was discovered that LibVNCServer incorrectly handled region clipping. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2020-14397) It was discovered that LibVNCServer did not properly reset incorrectly terminated TCP connections. A remote attacker could possibly use this issue to cause an infinite loop, resulting in a denial of service. (CVE-2020-14398) It was discovered that LibVNCServer did not properly access byte-aligned data. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2020-14399, CVE-2020-14400) It was discovered that LibVNCServer incorrectly handled screen scaling on the server side. A remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2020-14401) It was discovered that LibVNCServer incorrectly handled encodings. A remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2020-14402, CVE-2020-14403, CVE-2020-14404) It was discovered that LibVNCServer incorrectly handled TextChat messages. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2020-14405)

It was discovered that LibVNCServer incorrectly handled decompressing data. An attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2019-15680) It was discovered that an information disclosure vulnerability existed in LibVNCServer when sending a ServerCutText message. An attacker could possibly use this issue to expose sensitive information. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15681) It was discovered that LibVNCServer incorrectly handled cursor shape updates. If a user were tricked in to connecting to a malicious server, an attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15690, CVE-2019-20788) It was discovered that LibVNCServer incorrectly handled decoding WebSocket frames. An attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2017-18922)

It was discovered that LibVNCServer incorrectly handled certain operations. A remote attacker able to connect to applications using LibVNCServer could possibly use this issue to obtain sensitive information, cause a denial of service, or execute arbitrary code.

Last updated 24 July 2024

Last updated 24 July 2024

Last updated 24 July 2024

Integer overflow in the MallocFrameBuffer function in vncviewer.c in L ...

Nicolas Ruff discovered that LibVNCServer incorrectly handled memory when being advertised large screen sizes by the server. If a user were tricked into connecting to a malicious server, an attacker could use this issue to cause a denial of service, or possibly execute arbitrary code. (CVE-2014-6051, CVE-2014-6052) Nicolas Ruff discovered that LibVNCServer incorrectly handled large ClientCutText messages. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service. (CVE-2014-6053) Nicolas Ruff discovered that LibVNCServer incorrectly handled zero scaling factor values. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service. (CVE-2014-6054) Nicolas Ruff discovered that LibVNCServer incorrectly handled memory in the file transfer feature. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2014-6055)

Last updated 24 July 2024

Two stack-based buffer overflow flaws were reported in LibVNCServer's file transfer handling. A VNC client could use these flaws to cause the VNC server to crash or, potentially, execute arbitrary code.

Upstream commits:

https://github.com/newsoft/libvncserver/commit/06ccdf016154fde8eccb5355613ba04c59127b2e

https://github.com/newsoft/libvncserver/commit/f528072216dec01cee7ca35d94e171a3b909e677

auth.c in LibVNCServer 0.7.1 allows remote attackers to bypass authentication via a request in which the client specifies an insecure security type such as "Type 1 - None", which is accepted even if it is not offered by the server, a different issue than CVE-2006-2369.