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CVE-2026-18217

Keycloak-services: keycloak-services: saml http-redirect binding response preserves query string leading to parameter pollution

3.4 Low

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
None

Exploit likelihood

0.52%Up 0.3 points since Jul 31, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.4

Keycloak-services: keycloak-services: saml http-redirect binding response preserves query string leading to parameter pollution

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Record
CVE-2026-18217
CVSS 3.1
3.4 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-20
Updated
2026-11-06
EUVDEUVD-2026-51479 3.4

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Record
EUVD-2026-51479
CVSS 3.1
3.4 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
Updated
2026-11-06
GitHub AdvisoriesGHSA-82v3-6227-jc8x 3.4

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and...

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Record
GHSA-82v3-6227-jc8x
CVSS 3.1
3.4 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-20
Updated
2026-11-06
NVD 3.4

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Record
CVE-2026-18217
CVSS 3.1
3.4 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N
CVSS 3.1
4.7 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-20
Updated
2026-11-06

Affected products

History

History
RecordedChangedSources
products, referencesCVE List
products, referencesEUVD, GitHub Advisories, NVD
products, referencesCVE List
facts, products, referencesEUVD
first indexedCVE List, EUVD, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-18217 is a low vulnerability (CVSS 3.4) in Red Hat Build Of Keycloak 26.4, published July 31, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.52%, the 44th percentile. No source names a fixed version.

References

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