How severe is CVE-2021-3523?

CVE-2021-3523 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 high, and availability none.

Is CVE-2021-3523 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3523?

CVE-2021-3523 affects Redhat Apicast. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3523?

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-2021-3523 published?

CVE-2021-3523 was published on 2022-04-27 and last updated on 2026-06-17.

CVE-2021-3523

CVE-2021-3523 is a high-severity vulnerability in Redhat Apicast 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-281.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (52nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-281
Affected product: Redhat Apicast
Published: 2022-04-27
Last modified: 2026-06-17

Description

A flaw was found in 3Scale APICast in versions prior to 2.11.0, where it incorrectly identified connections for reuse. This flaw allows an attacker to bypass security restrictions for an API request when hosting multiple APIs on the same IP address.

Frequently asked questions

What is CVE-2021-3523?: A flaw was found in 3Scale APICast in versions prior to 2.11.0, where it incorrectly identified connections for reuse. This flaw allows an attacker to bypass security restrictions for an API request when hosting multiple APIs on the same IP address.
How severe is CVE-2021-3523?: CVE-2021-3523 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 high, and availability none.
Is CVE-2021-3523 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3523?: CVE-2021-3523 affects Redhat Apicast. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3523?: 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-2021-3523 published?: CVE-2021-3523 was published on 2022-04-27 and last updated on 2026-06-17.

References

https://bugzilla.redhat.com/show_bug.cgi?id=1954805

Affected products (1)

cpe:2.3:a:redhat:apicast:*:*:*:*:*:*:*:*

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