CVE-2020-12267: setMarkdown in Qt before 5.14.2 has a use-after-free related to QTextMarkdownImporter::insertBlock.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2020-12267 is a critical-severity flaw (CVSS 9.8) affecting qt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

setMarkdown in Qt before 5.14.2 has a use-after-free related to QTextMarkdownImporter::insertBlock.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-416
Published	2020-04-27
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: qt

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

Am I affected?

Timeline

2020-04-27 02:15 UTCPublished CVE record published
2026-06-17 02:51 UTCUpdated Record last modified

qt qt DOWNGRADE

Affected: 5.14.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.14.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 5.14.1 (Debian / Ubuntu)

apt-cache madison qt sudo apt install qt=<VERSION_BEFORE_5.14.1> sudo apt-mark hold qt

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

dnf --showduplicates list qt sudo dnf downgrade qt-<VERSION_BEFORE_5.14.1> sudo dnf versionlock add qt

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.

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-2020-12267?

qt: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-12267 being exploited?

CVE-2020-12267 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-2020-12267 affect?

CVE-2020-12267 affects qt. Severity is critical (CVSS 9.8). setMarkdown in Qt before 5.14.2 has a use-after-free related to QTextMarkdownImporter::insertBlock.

How urgent is CVE-2020-12267?

Priority 65/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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