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Fencer Vulns
critical 9.8

CVE-2016-7943 json

The XListFonts function in X.org libX11 before 1.6.4 might allow remote X servers to gain privileges via vectors involving length fields, w…

published 2016-12-13 9 y ago modified 2026-06-17 4 mo ago also EUVD-2016-8792

cvss
9.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.5%
EPSS 4.5% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

The XListFonts function in X.org libX11 before 1.6.4 might allow remote X servers to gain privileges via vectors involving length fields, which trigger out-of-bounds write operations.

Patch / fix

  • libx11 Debian 14, Debian 13, Debian 12 2:1.6.4-1

debian advisories DEBIAN-CVE-2016-7943

  • libx11 Ubuntu 14.04 LTS 2:1.6.2-1ubuntu2.1
  • libx11 Ubuntu 16.04 LTS 2:1.6.3-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2016-7943

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libx11 Alpine 3.2 1.6.3-r1
  • libx11 Alpine 3.3 1.6.3-r3

alpine advisories ALPINE-CVE-2016-7943

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-7943 updated cvss 5.0

libX11: Insufficient validation of server responses in FontNames

  • Red Hat Enterprise Linux 5 libX11 Red Hat Enterprise Linux 6 libX11, libX11-common Red Hat Enterprise Linux 7 libX11, libX11-common
    affected: no fix planned “Will not fix”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.46% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.