SB2017051638 - Fedora 25 update for libvncserver
Published: May 16, 2017 Updated: April 24, 2025
Security Bulletin ID
SB2017051638
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities
2
Exploitation vector
Remote access
Highest impact
Code execution
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 2 vulnerabilities.
1) Heap-based buffer overflow (CVE-ID: CVE-2016-9941)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to execute arbitrary code on vulnerable client system.
A heap-based buffer overflow vulnerability exists due to boundary error in rfbproto.c in LibVNCClient software, which is bundled with LibVNCServer. A remote attacker can trick the victim to connect to malicious VNC server, send a specially crafted FramebufferUpdate message containing a subrectangle outside of the client drawing area and trigger buffer overflow.
Successful exploitation of the vulnerability may allow an attacker to execute arbitrary code on vulnerable VNC client.
2) Heap-based buffer overflow (CVE-ID: CVE-2016-9942)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to execute arbitrary code on vulnerable client system.
A heap-based buffer overflow vulnerability exists due to boundary error in ultra.c in LibVNCClient software, which is bundled with LibVNCServer. A remote attacker can trick the victim to connect to malicious VNC server, send a specially crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions, and trigger buffer overflow.
Successful exploitation of the vulnerability may allow an attacker to execute arbitrary code on vulnerable VNC client.
Remediation
Install update from vendor's website.