CVE-2018-16428: In GNOME GLib 2.56.1, g_markup_parse_context_end_parse() in gmarkup.c has a NULL pointer dereference.

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CRITICAL 9.8REMOTEWATCHLISTDOWNGRADEMITIGATE

CVE-2018-16428 is a critical-severity flaw (CVSS 9.8) affecting glib, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In GNOME GLib 2.56.1, g_markup_parse_context_end_parse() in gmarkup.c has a NULL pointer dereference.

Why this priority

Critical severity
EPSS top 8%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	4.7% (top 8%)
CISA exploited list	No
Weakness	CWE-476
Published	2018-09-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: canonical · gnome

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-09-04 00:29 UTCPublished CVE record published
2026-06-17 01:44 UTCUpdated Record last modified

gnome glib DOWNGRADE

Affected: 2.56.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.56.1

1. Check installed version

apt-cache policy glib || rpm -q glib || glib --version

2. No fixed release: DOWNGRADE to a release before 2.56.1 (Debian / Ubuntu)

apt-cache madison glib sudo apt install glib=<VERSION_BEFORE_2.56.1> sudo apt-mark hold glib

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list glib sudo dnf downgrade glib-<VERSION_BEFORE_2.56.1> sudo dnf versionlock add glib

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

canonical ubuntu linux MITIGATE

Affected: 12.04 · 14.04 · 16.04 · 18.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · copyparty · FIXED · 1.20.26-1.fc46 · FEDORA-2026-8fbe18458e · source

sudo dnf upgrade --advisory=FEDORA-2026-8fbe18458e

Fedora ELN · man-pages · FIXED · 6.20-1.eln159 · FEDORA-2026-f1f5fb11b4 · source

sudo dnf upgrade --advisory=FEDORA-2026-f1f5fb11b4

Debian 12 · glib2.0 · FIXED · 2.58.0-1

sudo apt update && sudo apt install --only-upgrade glib2.0 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' glib2.0)" ge "2.58.0-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · glib2.0 · FIXED · 2.58.0-1

sudo apt update && sudo apt install --only-upgrade glib2.0 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' glib2.0)" ge "2.58.0-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 5 · firefox · DEFERRED

RHEL 5 · glib2 · DEFERRED

RHEL 6 · firefox · DEFERRED

RHEL 6 · glib2 · DEFERRED

RHEL 6 · thunderbird · DEFERRED

Amazon Linux 2 · see advisory · FIXED · ALAS2-2023-2049 · source

sudo yum update --advisory=ALAS2-2023-2049

Amazon Linux 1 · see advisory · FIXED · ALAS-2023-1742 · source

sudo yum update --advisory=ALAS-2023-1742

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: usn.ubuntu.com/3767-1/

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-16428?

glib: downgrade or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-16428 being exploited?

CVE-2018-16428 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-16428 affect?

CVE-2018-16428 affects glib, ubuntu linux. Severity is critical (CVSS 9.8). In GNOME GLib 2.56.1, g_markup_parse_context_end_parse() in gmarkup.c has a NULL pointer dereference.

How urgent is CVE-2018-16428?

Priority 72/100. Critical severity; EPSS top 8%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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