CVE-2021-22920: A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (former

Routine

MEDIUM 6.5DOWNGRADEDOWNGRADE

CVE-2021-22920 is a medium-severity flaw (CVSS 6.5) affecting application delivery management, 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 a phishing attack through a SAML authentication hijack to steal a valid user session.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-284
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 management DOWNGRADE

Affected: 12.1-62.25 · 13.0-82.42

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.1-62.25

1. Check installed version

apt-cache policy application-delivery-management || rpm -q application-delivery-management || application-delivery-management --version

2. No fixed release: DOWNGRADE to a release before 12.1-62.25 (Debian / Ubuntu)

apt-cache madison application-delivery-management sudo apt install application-delivery-management=<VERSION_BEFORE_12.1-62.25> sudo apt-mark hold application-delivery-management

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

dnf --showduplicates list application-delivery-management sudo dnf downgrade application-delivery-management-<VERSION_BEFORE_12.1-62.25> sudo dnf versionlock add application-delivery-management

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 gateway DOWNGRADE

Affected: 12.1-62.25 · 13.0-82.42

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.1-62.25

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 12.1-62.25 (Debian / Ubuntu)

apt-cache madison gateway sudo apt install gateway=<VERSION_BEFORE_12.1-62.25> sudo apt-mark hold gateway

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

dnf --showduplicates list gateway sudo dnf downgrade gateway-<VERSION_BEFORE_12.1-62.25> 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.

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-2021-22920?

application delivery management: downgrade or apply the listed mitigation; gateway: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-22920 being exploited?

CVE-2021-22920 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-2021-22920 affect?

CVE-2021-22920 affects application delivery management, gateway. Severity is medium (CVSS 6.5). 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-2021-22920?

Priority 38/100. No elevated risk signals yet.

Software pages

Citrix vulnerabilities

Related CVEs

CVE-2022-27512 MEDIUM 5.3 UPGRADE Temporary disruption of the ADM license service
CVE-2022-27511 HIGH 8.1 UPGRADE Corruption of the system by a remote, unauthenticated user

References

← Back to latest CVEs