CVE-2020-13962: Qt 5.12.2 through 5.14.2, as used in unofficial builds of Mumble 1.3.0 and other products, mishandles OpenSSL'

This week

HIGH 7.5REMOTEWATCHLISTDOWNGRADEUPGRADEMITIGATE

CVE-2020-13962 is a high-severity flaw (CVSS 7.5) affecting mumble, qt, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Qt 5.12.2 through 5.14.2, as used in unofficial builds of Mumble 1.3.0 and other products, mishandles OpenSSL's error queue, which can cause a denial of service to QSslSocket users. Because errors leak in unrelated TLS sessions, an unrelated session may be disconnected when any handshake fails. (Mumble 1.3.1 is not affected, regardless of the Qt version.)

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.1% (top 12%)
CISA exploited list	No
Published	2020-06-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · mumble · opensuse · qt

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

Am I affected?

Timeline

2020-06-09 00:15 UTCPublished CVE record published
2026-06-17 02:54 UTCUpdated Record last modified

mumble mumble DOWNGRADE

Affected: 1.3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.3.0 (Debian / Ubuntu)

apt-cache madison mumble sudo apt install mumble=<VERSION_BEFORE_1.3.0> sudo apt-mark hold mumble

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

dnf --showduplicates list mumble sudo dnf downgrade mumble-<VERSION_BEFORE_1.3.0> sudo dnf versionlock add mumble

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.

qt qt UPGRADE

Affected: >= 5.12.2 and < 5.12.9 · >= 5.13.0 and <= 5.13.2 · >= 5.14.0 and <= 5.14.2

Fixed in: 5.12.9

Safe to downgrade to: a release before 5.12.2

1. Check installed version

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

2. UPGRADE to 5.12.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade qt

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade qt

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.12.2 (Debian / Ubuntu)

apt-cache madison qt sudo apt install qt=<VERSION_BEFORE_5.12.2> sudo apt-mark hold qt

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list qt sudo dnf downgrade qt-<VERSION_BEFORE_5.12.2> 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.

fedoraproject fedora MITIGATE

Affected: 31 · 32 · 33

Fixed in: no fixed release known

Safe to downgrade to: a release before 31

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.

opensuse leap MITIGATE

Affected: 15.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 15.2

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.

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-2020-13962?

mumble: downgrade or apply the listed mitigation; qt: upgrade to 5.12.9; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-13962 being exploited?

CVE-2020-13962 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-2020-13962 affect?

CVE-2020-13962 affects mumble, qt, fedora. Severity is high (CVSS 7.5). Qt 5.12.2 through 5.14.2, as used in unofficial builds of Mumble 1.3.0 and other products, mishandles OpenSSL's error queue, which can cause a denial of service to QSslSocket users. Because errors leak in unrelated TLS sessions, an unrelate

How urgent is CVE-2020-13962?

Priority 63/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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