CVE-2026-4366

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Last Modified: UTC

Moderate Moderate Impact What does this mean?
5.8 CVSS v3 Base Score

Description

A flaw was identified in Keycloak, an identity and access management solution, where it improperly follows HTTP redirects when processing certain client configuration requests. This behavior allows an attacker to trick the server into making unintended requests to internal or restricted resources. As a result, sensitive internal services such as cloud metadata endpoints could be accessed. This issue may lead to information disclosure and enable attackers to map internal network infrastructure.

Statement

MODERATE impact: Keycloak is vulnerable to a blind Server-Side Request Forgery (SSRF) due to improper handling of HTTP redirects during client configuration. An attacker can exploit this remotely without authentication or user interaction by crafting a sector_identifier_uri that redirects to internal resources, potentially leading to information disclosure and internal network reconnaissance.

Mitigation

To mitigate this vulnerability, restrict the outbound network access of the Keycloak instance. Configure firewall rules to prevent the Keycloak server from initiating connections to internal network segments, especially to well-known cloud metadata service IP addresses such as `169.254.169.254`. For example, on Red Hat Enterprise Linux, you can use `firewalld` to add a rich rule:
`sudo firewall-cmd --permanent --zone=public --add-rich-rule='rule family="ipv4" destination address="169.254.169.254" reject'`
`sudo firewall-cmd --reload`
This may impact other services if they legitimately rely on accessing these internal IPs. Additionally, ensure that any configured `sector_identifier_uri` values are thoroughly validated to only point to trusted, external URLs that do not perform redirects to internal resources.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2026-4366

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2026-4366

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Build of Keycloak rhbk/keycloak-operator-bundle Fix deferred
Red Hat Build of Keycloak rhbk/keycloak-rhel9-operator Fix deferred
Red Hat JBoss Enterprise Application Platform 8 keycloak-services Fix deferred
Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-services Fix deferred
Red Hat Single Sign-On 7 keycloak-services Fix deferred
Red Hat build of Keycloak 26.4 rhbk/keycloak-operator-bundle Fixed RHSA-2026:19597
Red Hat build of Keycloak 26.4 rhbk/keycloak-rhel9 Fixed RHSA-2026:19597
Red Hat build of Keycloak 26.4 rhbk/keycloak-rhel9-operator Fixed RHSA-2026:19597
Red Hat build of Keycloak 26.4.12 Fixed RHSA-2026:19596
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 5.8
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Changed
Confidentiality Impact Low
Integrity Impact None
Availability Impact None

CVSS v3 Vector

Red Hat CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

Acknowledgements

Red Hat would like to thank Georgije Vukov (Elite Security Systems) for reporting this issue.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.