CVE-2025-68665: LangChain serialization injection vulnerability enables secret extraction

Attackers who control serialized data can extract environment variable secrets by injecting {"lc": 1, "type": "secret", "id": ["ENV_VAR"]} to load environment variables during deserialization (when secretsFromEnv: true). They can also instantiate classes with controlled parameters by injecting constructor structures to instantiate any class within the provided import maps with attacker-controlled parameters, potentially triggering side effects such as network calls or file operations.

Key severity factors:

• Affects the serialization path—applications trusting their own serialization output are vulnerable
• Enables secret extraction when combined with secretsFromEnv: true
• LLM responses in additional_kwargs can be controlled via prompt injection