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CVE-2018-20749

32
FAUCET Score

CVE-2018-20749 is a critical heap out-of-bounds write vulnerability in LibVNC versions prior to 0.9.12, affecting products from vendors like Canonical, Debian, and Siemens. With a CVSS score of 9.8, it allows unauthenticated attackers to achieve high impact on confidentiality, integrity, and availability over the network with low complexity. While the vulnerability is severe and has a high FAUCET Risk Score, there is currently no evidence of active exploitation, public exploit code, or significant community discussion.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.9.12CPE matchmatch criteria
cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
18.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.23%
Probability of exploitation in next 30 days
EPSS Percentile
86.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
This CVE's current EPSS score of 0.0323 is in the 79th percentile among its peer group of 36,821 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: libvncserver

Vendor Advisories (1)

redhatCVE-2018-20749Important

libvncserver: Heap out-of-bounds write in rfbserver.c in rfbProcessFileTransferReadBuffer() allows for potential code execution (Incomplete fix for CVE-2018-15127)

Jan 6, 2019

References

cert-portal.siemens.com / productcert/pdf/ssa-390195.pdf
PatchThird Party Advisory
github.com / LibVNC/libvncserver/commit/15bb719c03cc70f14c36a843dcb16ed69b405707
PatchThird Party Advisory
github.com / LibVNC/libvncserver/issues/273
Issue TrackingThird Party Advisory
lists.debian.org / debian-lts-announce/2019/01/msg00029.html
Third Party Advisory
lists.debian.org / debian-lts-announce/2019/10/msg00042.html
Mailing ListThird Party Advisory
usn.ubuntu.com / 3877-1
Third Party Advisory
usn.ubuntu.com / 4547-1
Third Party Advisory
usn.ubuntu.com / 4587-1
Third Party Advisory
openwall.com / lists/oss-security/2018/12/10/8
ExploitMailing ListThird Party Advisory
securityfocus.com / bid/106825
Broken Link