What is CVE-2018-20750?

CVE-2018-20750 is a critical-severity vulnerability in Libvnc Project Libvncserver, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-01-30.

How severe is CVE-2018-20750?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2018-20750 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Libvnc Project Libvncserver

CVE-2018-20750

LibVNC through 0.9.12 contains a heap out-of-bounds write vulnerability in libvncserver/rfbserver.c. The fix for CVE-2018-15127 was incomplete.

Vulnerability class: Buffer Overflow

Published 2019-01-30 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.033 (88.2th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 88.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.033 · newest: 0.033 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

Public proof-of-concept exploits

ARPSyndicate/cve-scores

References

lists.debian.org/debian-lts-announce/2019/01/msg00029.html (mailing-list, Mailing List, Third Party Advisory)
www.securityfocus.com/bid/106825 (vdb-entry, Broken Link)
github.com/LibVNC/libvncserver/issues/273 (Third Party Advisory, Issue Tracking)
github.com/LibVNC/libvncserver/commit/09e8fc02f59f16e2583b34fe1a270c238bd9ffec (Patch, Third Party Advisory)
usn.ubuntu.com/3877-1/ (vendor-advisory, Third Party Advisory)
www.openwall.com/lists/oss-security/2018/12/10/8 (Exploit, Mailing List, Third Party Advisory)
lists.debian.org/debian-lts-announce/2019/10/msg00042.html (mailing-list, Mailing List, Third Party Advisory)
usn.ubuntu.com/4547-1/ (vendor-advisory, Third Party Advisory)
usn.ubuntu.com/4587-1/ (vendor-advisory, Third Party Advisory)
cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2018-20750?: CVE-2018-20750 is a critical-severity vulnerability in Libvnc Project Libvncserver, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-01-30.
How severe is CVE-2018-20750?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2018-20750 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.