CVE-2022-21716: Twisted is an event-based framework for internet applications, supporting Python 3.6+

This week

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2022-21716 is a high-severity flaw (CVSS 7.5) affecting twisted, debian linux, http server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 22.2.0, Twisted SSH client and server implement is able to accept an infinite amount of data for the peer's SSH version identifier. This ends up with a buffer using all the available memory. The attach is a simple as `nc -rv localhost 22 < /dev/zero`. A patch is available in version 22.2.0. There are currently no known workarounds.

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	3.5% (top 11%)
CISA exploited list	No
Weakness	CWE-120, CWE-770
Published	2022-03-03
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: debian · fedoraproject · oracle · twisted

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

Am I affected?

Timeline

2022-03-03 21:15 UTCPublished CVE record published
2026-06-17 04:26 UTCUpdated Record last modified

twisted twisted UPGRADE

Affected: >= 21.7.0 and < 22.2.0

Fixed in: 22.2.0

Safe to downgrade to: a release before 21.7.0

1. Check installed version

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

2. UPGRADE to 22.2.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade twisted

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 21.7.0 (Debian / Ubuntu)

apt-cache madison twisted sudo apt install twisted=<VERSION_BEFORE_21.7.0> sudo apt-mark hold twisted

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

dnf --showduplicates list twisted sudo dnf downgrade twisted-<VERSION_BEFORE_21.7.0> sudo dnf versionlock add twisted

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.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

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.

oracle http server DOWNGRADE

Affected: 12.2.1.3.0 · 12.2.1.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.2.1.3.0

1. Check installed version

apt-cache policy http-server || rpm -q http-server || http-server --version

2. No fixed release: DOWNGRADE to a release before 12.2.1.3.0 (Debian / Ubuntu)

apt-cache madison http-server sudo apt install http-server=<VERSION_BEFORE_12.2.1.3.0> sudo apt-mark hold http-server

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

dnf --showduplicates list http-server sudo dnf downgrade http-server-<VERSION_BEFORE_12.2.1.3.0> sudo dnf versionlock add http-server

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.

oracle zfs storage appliance kit DOWNGRADE

Affected: 8.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.8

1. Check installed version

apt-cache policy zfs-storage-appliance-kit || rpm -q zfs-storage-appliance-kit || zfs-storage-appliance-kit --version

2. No fixed release: DOWNGRADE to a release before 8.8 (Debian / Ubuntu)

apt-cache madison zfs-storage-appliance-kit sudo apt install zfs-storage-appliance-kit=<VERSION_BEFORE_8.8> sudo apt-mark hold zfs-storage-appliance-kit

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

dnf --showduplicates list zfs-storage-appliance-kit sudo dnf downgrade zfs-storage-appliance-kit-<VERSION_BEFORE_8.8> sudo dnf versionlock add zfs-storage-appliance-kit

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: 35 · 36

Fixed in: no fixed release known

Safe to downgrade to: a release before 35

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-2022-21716?

twisted: upgrade to 22.2.0; debian linux: mitigate or apply the listed mitigation; http server: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-21716 being exploited?

CVE-2022-21716 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-2022-21716 affect?

CVE-2022-21716 affects twisted, debian linux, http server. Severity is high (CVSS 7.5). Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 22.2.0, Twisted SSH client and server implement is able to accept an infinite amount of data for the peer's SSH version identifier. This ends up

How urgent is CVE-2022-21716?

Priority 64/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Python vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2026-42304 HIGH 7.5 UPGRADE Twisted is an event-based framework for internet applications, supporting Python 3.6+
CVE-2024-41810 MEDIUM 6.1 UPGRADE Twisted is an event-based framework for internet applications, supporting Python 3.6+
CVE-2023-46137 MEDIUM 5.3 UPGRADE Twisted is an event-based framework for internet applications
CVE-2022-39348 MEDIUM 5.4 UPGRADE MITIGATE Twisted is an event-based framework for internet applications
CVE-2022-24801 HIGH 8.1 UPGRADE MITIGATE Twisted is an event-based framework for internet applications, supporting Python 3.6+

References

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