CVE-2026-19505 [CRITICAL] – Improper cryptographic signature verification in `jst_functions.c` in RDK-B WebUI `rdkb-20

Improper cryptographic signature verification in `jst_functions.c` in RDK-B WebUI `rdkb-2025q4-kirkstone.04.10.26` allows a remote attacker to bypass authentication and obtain administrative access via a forged JWT containing an invalid RSA signature.