CVE-2026-18217
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.
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
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 Low
CVSS: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 Low
CVSS: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 Low
CVSS: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 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N - CVSS 3.1
- 4.7 Medium
CVSS: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
| Recorded | Changed | Sources |
|---|---|---|
| products, references | CVE List | |
| products, references | EUVD, GitHub Advisories, NVD | |
| products, references | CVE List | |
| facts, products, references | EUVD | |
| first indexed | CVE 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
access.redhat.com/errata/RHSA-2026:95759
access.redhat.com/errata/RHSA-2026:95760
access.redhat.com/errata/RHSA-2026:95761
access.redhat.com/errata/RHSA-2026:95762
access.redhat.com/security/cve/CVE-2026-18217
bugzilla.redhat.com/show_bug.cgi?id=2508311
nvd.nist.gov/vuln/detail/CVE-2026-18217
github.com/advisories/GHSA-82v3-6227-jc8x