# AN-2026-0623: LangChain langchain-core dumps()/loads() serialization injection leaks env secrets (CVE-2025-68664): upgrade to 1.2.5 / 0.3.81; load() defaults changed

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- id: AN-2026-0623 (version 1; cite https://breakwire.org/claim/AN-2026-0623/v/1)
- kind: advisory · status: active · review: editor
- source: <https://github.com/advisories/GHSA-c67j-w6g6-q2cm>
- more sources: <https://github.com/langchain-ai/langchain/security/advisories/GHSA-c67j-w6g6-q2cm> <https://github.com/langchain-ai/langchain/releases/tag/langchain-core%3D%3D1.2.5> <https://github.com/langchain-ai/langchain/releases/tag/langchain-core%3D%3D0.3.81> <https://nvd.nist.gov/vuln/detail/CVE-2025-68664>
- event date: 2025-12-23
- services: langchain
- affected: pip:langchain-core >= 1.0.0, < 1.2.5; pip:langchain-core < 0.3.81
- fixed in: langchain-core 1.2.5; langchain-core 0.3.81
- severity: critical
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. GHSA-c67j-w6g6-q2cm / CVE-2025-68664 (critical, CVSS 3.1 9.3, CWE-502), published 2025-12-23: langchain-core dumps() and dumpd() did not escape free-form dictionaries containing the internal 'lc' key, so user-controlled data with that structure was treated as a LangChain object when later deserialized with load() or loads().  [✓0 ✗0]
1. Per the advisory, an attacker who controls serialized data can inject {"lc": 1, "type": "secret", "id": ["ENV_VAR"]} to read environment-variable secrets (when secrets_from_env=True, the old default) or instantiate Serializable classes in the trusted namespaces with attacker-controlled parameters. The most common vector is LLM response fields such as additional_kwargs or response_metadata, controllable through prompt injection.  [✓0 ✗0]
2. Affected uses listed in the advisory include astream_events(version="v1") (v2 is not vulnerable), Runnable.astream_log(), RunnableWithMessageHistory, load()/loads() of untrusted data, InMemoryVectorStore.load(), langchain-community caches, hub.pull, StringRunEvaluatorChain, create_lc_store / create_kv_docstore, MultiVectorRetriever byte stores and LangSmithRunChatLoader.  [✓0 ✗0]
3. Affected: pip:langchain-core >= 1.0.0, < 1.2.5 and < 0.3.81. Patched: langchain-core 1.2.5 and 0.3.81.  [✓0 ✗0]
4. The patch is a breaking change for some load()/loads() callers: a new allowed_objects parameter defaults to 'core' (allowlist), secrets_from_env now defaults to False instead of True, and a new init_validator blocks Jinja2 templates by default. Standard LangChain types (messages, documents, prompts, partner integrations) need no change.  [✓0 ✗0]

## Fix
```text
Upgrade langchain-core to 1.2.5 (1.x) or 0.3.81 (0.3.x). Switch astream_events to version="v2". After upgrading, if deserializing custom classes fails, pass them explicitly with load(data, allowed_objects=[MyClass]); if code relied on secrets loading from the environment, pass secrets_from_env=True only for trusted data; Jinja2 prompt templates need init_validator=None and must only be used with trusted data.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0623/reports_

## History
- v1 2026-10-29 by wire-editor: promoted from candidate #66 (gh-advisories-agent-frameworks) after review