CVE-2021-22919: A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (former

Q: How do I fix CVE-2021-22919?

application delivery controller firmware: upgrade to 11.1-65.22, 12.1-55.238, 12.1-62.27, 13.0-82.45; gateway: upgrade to 12.1-62.27, 13.0-82.45; netscaler gateway: upgrade to 11.1-65.22. Exact commands for each OS are on this page.

Q: Is CVE-2021-22919 being exploited?

CVE-2021-22919 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-22919 affect?

CVE-2021-22919 affects application delivery controller firmware, gateway, netscaler gateway. Severity is high (CVSS 7.5). A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (formerly known as NetScaler Gateway), and Citrix SD-WAN WANOP Edition models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabiliti

Q: How urgent is CVE-2021-22919?

Priority 46/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADEUPGRADEUPGRADE

CVE-2021-22919 is a high-severity flaw (CVSS 7.5) affecting application delivery controller firmware, gateway, netscaler gateway. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (formerly known as NetScaler Gateway), and Citrix SD-WAN WANOP Edition models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabilities, if exploited, could lead to the limited available disk space on the appliances being fully consumed.

Why this priority

High severity
Remotely exploitable, no login, no user action

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	0.9% (top 39%)
CISA exploited list	No
Weakness	CWE-770
Published	2021-08-05
Last modified	2026-06-17

Publisher (CNA): HackerOne · Vendor: citrix

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

Am I affected?

Timeline

2021-08-05 21:15 UTCPublished CVE record published
2026-06-17 03:38 UTCUpdated Record last modified

citrix application delivery controller firmware UPGRADE

Affected: >= 11.1 and < 11.1-65.22 · >= 12.1 and < 12.1-62.27 · >= 13.0 and < 13.0-82.45 · >= 12.1 and < 12.1-55.238

Fixed in: 11.1-65.22, 12.1-55.238, 12.1-62.27, 13.0-82.45

Safe to downgrade to: a release before 11.1

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.

citrix gateway UPGRADE

Affected: >= 12.1 and < 12.1-62.27 · >= 13.0 and < 13.0-82.45

Fixed in: 12.1-62.27, 13.0-82.45

Safe to downgrade to: a release before 12.1

1. Check installed version

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

2. UPGRADE to 12.1-62.27 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade gateway

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 12.1 (Debian / Ubuntu)

apt-cache madison gateway sudo apt install gateway=<VERSION_BEFORE_12.1> sudo apt-mark hold gateway

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

dnf --showduplicates list gateway sudo dnf downgrade gateway-<VERSION_BEFORE_12.1> sudo dnf versionlock add gateway

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.

citrix netscaler gateway UPGRADE

Affected: >= 11.1 and < 11.1-65.22

Fixed in: 11.1-65.22

Safe to downgrade to: a release before 11.1

1. Check installed version

apt-cache policy netscaler-gateway || rpm -q netscaler-gateway || netscaler-gateway --version

2. UPGRADE to 11.1-65.22 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade netscaler-gateway

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade netscaler-gateway

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 11.1 (Debian / Ubuntu)

apt-cache madison netscaler-gateway sudo apt install netscaler-gateway=<VERSION_BEFORE_11.1> sudo apt-mark hold netscaler-gateway

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

dnf --showduplicates list netscaler-gateway sudo dnf downgrade netscaler-gateway-<VERSION_BEFORE_11.1> sudo dnf versionlock add netscaler-gateway

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.

citrix sd-wan wanop UPGRADE

Affected: >= 10.2 and < 10.2.9.b · >= 11.2 and < 11.2.3.b · >= 11.3 and < 11.3.2.a · >= 11.4 and < 11.4.0.a

Fixed in: 10.2.9.b, 11.2.3.b, 11.3.2.a, 11.4.0.a

Safe to downgrade to: a release before 10.2

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-2021-22919?

application delivery controller firmware: upgrade to 11.1-65.22, 12.1-55.238, 12.1-62.27, 13.0-82.45; gateway: upgrade to 12.1-62.27, 13.0-82.45; netscaler gateway: upgrade to 11.1-65.22. Exact commands for each OS are on this page.

Is CVE-2021-22919 being exploited?

CVE-2021-22919 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-2021-22919 affect?

CVE-2021-22919 affects application delivery controller firmware, gateway, netscaler gateway. Severity is high (CVSS 7.5). A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (formerly known as NetScaler Gateway), and Citrix SD-WAN WANOP Edition models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabiliti

How urgent is CVE-2021-22919?

Priority 46/100. High severity; Remotely exploitable, no login, no user action

Software pages

Citrix vulnerabilities

Related CVEs

CVE-2019-19781 CRITICAL 9.8 EXPLOITED MITIGATE MITIGATE Citrix ADC, Gateway, and SD-WAN WANOP Appliance Code Execution Vulnerability
CVE-2022-27518 CRITICAL 9.8 EXPLOITED UPGRADE UPGRADE Citrix Application Delivery Controller (ADC) and Gateway Authentication Bypass Vulnerability
CVE-2022-27516 MEDIUM 5.3 UPGRADE UPGRADE User login brute force protection functionality bypass
CVE-2022-27513 HIGH 8.3 UPGRADE UPGRADE Remote desktop takeover via phishing
CVE-2022-27510 CRITICAL 9.8 UPGRADE UPGRADE Unauthorized access to Gateway user capabilities

References

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