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GHSA-rr5q-3xwr-f323

Keycloak Vulnerable to Improper Validation of Specified Quantity in Input

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-9704

Packages

EcosystemPackageAffectedFixed in
Maven org.keycloak:keycloak-server-spi-private < 26.6.3 26.6.3
Maven org.keycloak:keycloak-services < 26.6.3 26.6.3

Details

As written in the advisory (Markdown source, shown as plain text).

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

References

External links from the advisory. They lead to third-party sites.