How severe is CVE-2021-22956?

CVE-2021-22956 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-22956 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22956?

CVE-2021-22956 primarily affects Citrix Gateway. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-22956?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-22956 published?

CVE-2021-22956 was published on 2021-12-07 and last updated on 2026-06-17.

CVE-2021-22956

CVE-2021-22956 is a high-severity vulnerability in Citrix Gateway with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Citrix Gateway
Published: 2021-12-07
Last modified: 2026-06-17

Description

An uncontrolled resource consumption vulnerability exists in Citrix ADC <13.0-83.27, <12.1-63.22 and 11.1-65.23 that could allow an attacker with access to NSIP or SNIP with management interface access to cause a temporary disruption of the Management GUI, Nitro API, and RPC communication.

Frequently asked questions

What is CVE-2021-22956?: An uncontrolled resource consumption vulnerability exists in Citrix ADC <13.0-83.27, <12.1-63.22 and 11.1-65.23 that could allow an attacker with access to NSIP or SNIP with management interface access to cause a temporary disruption of the Management GUI, Nitro API, and RPC communication.
How severe is CVE-2021-22956?: CVE-2021-22956 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-22956 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22956?: CVE-2021-22956 primarily affects Citrix Gateway. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-22956?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-22956 published?: CVE-2021-22956 was published on 2021-12-07 and last updated on 2026-06-17.

References

https://support.citrix.com/article/CTX330728

Affected products (3)

cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
cpe:2.3:a:citrix:gateway:*:*:*:*:*:*:*:*
cpe:2.3:a:citrix:sd-wan:*:*:*:*:wanop:*:*:*

More vulnerabilities in Citrix Gateway

CVE-2022-27510 — Critical (CVSS 9.8): Unauthorized access to Gateway user capabilities
CVE-2020-8247 — High (CVSS 8.8): Citrix ADC and Citrix Gateway 13.0 before 13.0-64.35, Citrix ADC and NetScaler Gateway 12.1 before 12.1-58.15, Citrix…
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