Summary

The MariaDB and pgvector embedding stores build metadata-filter SQL by string-concatenating
filter keys (and, in MariaDB, string values) directly into the query without adequate
escaping. A crafted metadata key in EmbeddingSearchRequest.filter() can break out of its SQL
context and inject arbitrary SQL into the statements executed by the stores' search and
removeAll(Filter) operations.

Details

pgvector — JSON mode (default, COMBINED_JSON / COMBINED_JSONB). JSONFilterMapper
places the key inside a single-quoted SQL literal (the JSON key of the ->> operator) with no
escaping:

(metadata->>'<key>')::text

A key containing a single quote breaks out, e.g.
metadataKey("')::text IS NOT NULL OR pg_sleep(1) IS NOT NULL --") injects a live pg_sleep(1)
(observable as a delay; exploitable for blind data extraction).

pgvector — column mode (COLUMN_PER_KEY). ColumnFilterMapper used the key as a bare,
unquoted, unvalidated SQL identifier (<key>::<type>), so a key such as 1=1 OR true --
injects directly.

MariaDB — JSON mode (default). JSONFilterMapper placed the key inside the JSON path literal
'$.<key>' unescaped (same break-out mechanism). Additionally, MariaDbFilterMapper.formatValue()
escaped ' but not \; because MariaDB treats backslash as an escape character by default, a
string value ending in a backslash could also break out of its literal.

MariaDB — column mode (COLUMN_PER_KEY). ColumnFilterMapper fell back to the raw,
unescaped key when the driver could not quote it as an identifier (e.g. a
character).

The filter key is the runtime injection surface; both stores' search() (including pgvector's
HYBRID mode) and removeAll(Filter) are affected. Add/upsert operations a
parameterized and not affected.

Impact

Applications that allow attacker-influenced metadata filter keys (e.g. use
LLM-generated filters) to reach these stores are exposed to SQL injection: blind data
exfiltration, denial of service via sleep functions, and — through `remove
deletion of arbitrary rows. Applications using only hard-coded, developer-defined filter keys
are not reachable.

Patches

Fixed in langchain4j-mariadb and langchain4j-pgvector 1.16.3-beta26:

• JSON filter keys are escaped before being embedded in the SQL string lit
  quotes doubled, correct for PostgreSQL standard_conforming_strings = on; MariaDB: backslash
  and single quote).
• MariaDB string values escape both \ and '.
• Column-mode keys are validated/quoted as identifiers and rejected when u
  concatenated as raw SQL.

Workarounds

• Do not pass untrusted input as metadata filter keys.
• Restrict filter keys to a known allow-list at the application layer.

References

• pgvector: JSONFilterMapper, ColumnFilterMapper
• MariaDB: JSONFilterMapper, MariaDbFilterMapper, ColumnFilterMapper

References

• GHSA-2mfg-cc43-9pcj