SB2020070189 - Ubuntu update for libvncserver
Published: July 1, 2020 Updated: April 23, 2025
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 5 secuirty vulnerabilities.
1) NULL pointer dereference (CVE-ID: CVE-2019-15680)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a NULL pointer dereference error in "zlib.c" in the "HandleZlibBPP" function. A remote attacker can trigger denial of service conditions via network connectivity.
2) Memory leak (CVE-ID: CVE-2019-15681)
The vulnerability allows a remote attacker to gain access to sensitive information on the target system.
The vulnerability exists due memory leak in VNC server code. A remote attacker can read stack memory and disclose sensitive information.
Combined with another vulnerability, it can be used to leak stack memory and bypass ASLR.
3) Heap-based buffer overflow (CVE-ID: CVE-2019-15690)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to a boundary error. A remote attacker can trigger heap-based buffer overflow and execute arbitrary code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
4) Integer overflow (CVE-ID: CVE-2019-20788)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to integer overflow in libvncclient/cursor.c when processing large height or width values. A remote attacker can trick the victim to connect to a malicious VNC server, trigger integer overflow and execute arbitrary code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
5) Out-of-bounds write (CVE-ID: CVE-2017-18922)
The vulnerability allows a remote non-authenticated attacker to execute arbitrary code.
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.
Remediation
Install update from vendor's website.