CVE-2026-40087 LangChain has incomplete f-string validation in prompt templates

LangChain is a framework for building agents and LLM-powered applications. Prior to 0.3.84 and 1.2.28, LangChain's f-string prompt-template validation was incomplete in two respects. First, some prompt template classes accepted f-string templates and formatted them without enforcing the same...

CVE-2026-40087

LangChain CVE-2026-40087 affects the f-string prompt-template validation prior to versions 0.3.84 and 1.2.28. The vulnerability arises because DictPromptTemplate and ImagePromptTemplate could accept templates containing attribute access or indexing expressions and evaluate them during formatting,...