CVE-2018-20748

Exp

LibVNC before 0.9.12 contains multiple heap out-of-bounds write vulnerabilities in libvncclient/rfbproto.c. The fix for CVE-2018-20019 was incomplete.

Published: 2019-01-30 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-20748 is rated High Exploit Risk (86.6/100): CVSS Critical severity, with high exploitation likelihood (EPSS 10.57%, 93th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2018-20748

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2018-20748

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-12-31 10.72% 10.57% -0.15%
2 2025-12-28 8.04% 10.72% +2.68%
3 2025-12-27 — 8.04% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-20748

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2018-20748

OS Trackers for CVE-2018-20748

vendor priority summary link
alpine critical CVE-2018-20748: 1 source package rows (libvncserver); 4 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 4. https://security.alpinelinux.org/vuln/CVE-2018-20748
debian not yet assigned CVE-2018-20748 not yet assigned priority: Debian including 2 source packages (libvncserver, veyon), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 10. https://security-tracker.debian.org/tracker/CVE-2018-20748
redhat medium — https://access.redhat.com/security/cve/CVE-2018-20748
suse high CVE-2018-20748 severity important: SUSE including 22 source package names (LibVNCServer-0.9.1-160.9.1, LibVNCServer-devel-0.9.1-160.9.1, …), 85 product×package rows across 53 product lines (SUSE Enterprise Storage 4, SUSE Linux Enterprise High Performance Computing 12 SP5, … (53 product lines)): Fixed 85. https://www.suse.com/security/cve/CVE-2018-20748/
ubuntu medium CVE-2018-20748 medium priority: Ubuntu including 4 source packages (italc, libvncserver, tightvnc, x11vnc), 68 status rows across 18 suites (bionic, cosmic, disco, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 29, DNE 13, released 10, ignored 9, needs-triage 7. https://ubuntu.com/security/CVE-2018-20748

Affected software / configurations for CVE-2018-20748

Vendor Product Version Raw CPE
libvnc_project libvncserver < 0.9.12 cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
canonical ubuntu_linux 14.04 cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.10 cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
siemens simatic_itc1500_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc1500_firmware:*:*:*:*:*:*:*:*
siemens simatic_itc1500_pro_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc1500_pro_firmware:*:*:*:*:*:*:*:*
siemens simatic_itc1900_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc1900_firmware:*:*:*:*:*:*:*:*
siemens simatic_itc1900_pro_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc1900_pro_firmware:*:*:*:*:*:*:*:*
siemens simatic_itc2200_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc2200_firmware:*:*:*:*:*:*:*:*
siemens simatic_itc2200_pro_firmware >= 3.0.0.0, < 3.2.1.0 cpe:2.3:o:siemens:simatic_itc2200_pro_firmware:*:*:*:*:*:*:*:*

References for CVE-2018-20748

URL Tags
https://cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf Patch Third Party Advisory
https://github.com/LibVNC/libvncserver/commit/a64c3b37af9a6c8f8009d7516874b8d266b42bae Patch Third Party Advisory
https://github.com/LibVNC/libvncserver/commit/c2c4b81e6cb3b485fb1ec7ba9e7defeb889f6ba7 Patch Third Party Advisory
https://github.com/LibVNC/libvncserver/commit/c5ba3fee85a7ecbbca1df5ffd46d32b92757bc2a Patch Third Party Advisory
https://github.com/LibVNC/libvncserver/commit/e34bcbb759ca5bef85809967a268fdf214c1ad2c Patch Third Party Advisory
https://github.com/LibVNC/libvncserver/issues/273 Issue Tracking Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/01/msg00029.html Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html Mailing List Third Party Advisory
https://usn.ubuntu.com/3877-1/ Third Party Advisory
https://usn.ubuntu.com/4547-1/ Third Party Advisory
https://usn.ubuntu.com/4587-1/ Third Party Advisory
https://www.openwall.com/lists/oss-security/2018/12/10/8 Exploit Mailing List Third Party Advisory
cvelogic Threat Intelligence