CVE-2019-20839
libvncserver: buffer overflow in ConnectClientToUnixSock()
Severity
ModerateRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · June 17, 2020
Updated · January 14, 2026
Description
libvncclient/sockets.c in LibVNCServer before 0.9.13 has a buffer overflow via a long socket filename.
Statement
This is only an issue if the "ConnectClientToUnixSock()" function is used directly with an overly long socket name. It's more common that the "ConnectToRFBServer()" function is used, which would prevent exploiting this flaw as it performs additional checks. Additionally, the buffer overflow is caught by compiled-in buffer overflow checks, limiting the impact to a crash.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')