PYSEC-2026-3636 
## Summary

The Postgres and SQLite stores persist hierarchical namespaces as a dot-joined string (`("memories", "alice")` becomes `memories.alice`) and scoped reads by matching that string with `LIKE '<path>%'`. Because `LIKE` has no notion of the `.` separator, a scoped `search` or `list_namespaces` also matched sibling namespaces whose flattened form shares leading characters.

Applications commonly use the namespace as a tenant boundary. Where they do, a read scoped to one namespace could return items belonging to another, without any crafted input — an ordinary scoped request was sufficient.

We have no evidence of this behavior being exploited in the wild.

## Affected users / systems

You may be affected if you:

- use `PostgresStore`/`AsyncPostgresStore` or `SqliteStore`/`AsyncSqliteStore`, and
- rely on the namespace to separate data between users or tenants, and
- have namespace labels where one is a prefix of another (`1` and `12`, `alice` and `alice2`), or labels containing `_` or `%`

Applications whose namespace labels are fixed-length identifiers such as UUIDs, containing no `_` or `%`, are not affected — no such label can be a prefix of another. `InMemoryStore` compares namespaces element-wise and is not affected.

Three distinct cases were possible:

- **Sibling namespaces.** A read scoped to `("foo",)` also returned items under `("foobar",)` and `("foo2",)`.
- **Unescaped pattern metacharacters.** `_` and `%` are legal namespace labels — only `.` is rejected — but were interpolated into the match pattern unescaped, so `("user_1",)` also matched `("userX1",)`.
- **Suffix conditions.** `list_namespaces(suffix=("alice",))` also matched the sibling leaf `users.malice`.

This is not SQL injection. Values were passed as bound parameters and never interpolated into statement text; the bound value *was itself* a `LIKE` pattern whose metacharacters were not neutralized.

## Impact

- Confidentiality: disclosure of stored items belonging to namespaces outside the caller's intended scope, where namespaces are used as a tenant or user boundary.
- No integrity or availability impact. `get`, `put`, and `delete` compare namespaces with `=` and were never affected; the issue is limited to read paths.

## Patches / mitigation

Prefix scoping now matches the namespace exactly or requires the `.` separator before any remainder, pattern metacharacters in labels are escaped, and `list_namespaces` uses segment-aware matching for both prefix and suffix conditions.

On SQLite, the descendant match moved from `LIKE` to `GLOB`. `LIKE` is case-insensitive for ASCII in SQLite, so scoped reads previously matched namespaces differing only in case, while `get`/`put`/`delete` treated them as distinct. Search now agrees with them.

Upgrade to `langgraph-checkpoint-postgres` 3.1.1 or `langgraph-checkpoint-sqlite` 3.1.1.

## Compatibility

`*` in a `list_namespaces` match path now spans exactly one namespace segment. This restores the documented behavior — `NamespacePath` documents `("cache", "*", "v1")` as "any cache category with v1 version" — and matches `InMemoryStore`. Multi-segment matching was an artifact of translating `*` into a SQL `%` wildcard, the same mechanism responsible for this issue, and could not be preserved while fixing it.

Callers relying on the previous behavior can express "match at any depth" by combining both match conditions, which are ANDed:

```python
list_namespaces(prefix=["uid"], suffix=["alice"])
```

Applications whose namespace labels cannot be prefixes of one another see no behavioral change.

## Operational guidance

- Prefer fixed-length namespace labels such as UUIDs, so no label can be a prefix of another.
- Where labels are user-supplied, validate them at the boundary rather than relying on scoping alone.

## LangSmith / hosted deployments note

Unlike previous store advisories, this issue does reach hosted deployments. LangSmith deployments default to `LANGGRAPH_STORE_BACKEND=python`, which uses `AsyncPostgresStore` from `checkpoint-postgres`. Deployments configured with `LANGGRAPH_STORE_BACKEND=grpc` use a separate implementation that received an equivalent fix.
CVSS v3.1 score: 5.3