LangChain Critical CVE-2025-68664: Serialization Injection CVSS 9.3 + CVE-2025-68665 + CVE-2026-34070 Path Traversal

CRÍTICO: LangChain serialization injection (dumps/loads no escapan dicts con lc keys) - extrae secrets. CVSS 9.3. Patch 1.2.5 y 0.3.81. 52M downloads/semana.