CVE-2021-3523Network attack vector

Authorization bypass via cross-service connection reuse

Published Apr 27, 2022 · Updated Aug 3, 2024

Authorization bypass in Red Hat APIcast before 2.11.0 allows remote attackers to bypass API access restrictions through connection reuse. The upstream pool keyed reusable HTTPS connections by backend host without separating service identities, so an authorized connection could serve another API on the same IP address. Exposure requires multiple APIs on one IP address and persistent connection reuse; the bounded consequence is unauthorized API access.

CVSS severity7.5
High
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Red Hat APIcast before 2.11.0 allows remote attackers to bypass API access restrictions through connection reuse. The upstream pool keyed reusable HTTPS connections by backend host without separating service identities, so an authorized connection could serve another API on the same IP address. Exposure requires multiple APIs on one IP address and persistent connection reuse; the bounded consequence is unauthorized API access.

The record

CVE
CVE-2021-3523
Published
Apr 27, 2022
Updated
Aug 3, 2024
Vendor
Red Hat
Product
APIcast
Classifications
CWE-281, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 27, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3scale-apicast versions prior to 2.11.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Red Hat · APIcastversion=3scale-apicast versions prior to 2.11.0

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-281Improper Preservation of Permissions
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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