CVE-2026-18217

LOW
Published Jul 31, 2026 Modified Aug 3, 2026 CWE-20

Description

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.

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CVSS v3.1 Score

3.4
LOW
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0019
Probability of exploitation
0.09%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

References

Frequently Asked Questions

What is CVE-2026-18217? +
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. It has a CVSS v3.1 base score of 3.4 (LOW).
How severe is CVE-2026-18217? +
CVE-2026-18217 has a CVSS v3.1 score of 3.4 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0019, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2026-18217? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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