Security advisory PYSEC-2026-62: SQL injection vulnerability in geopandas before v.1.1.2 allows an attacker to obtain sensitive information via the to_postgis()` function being used to write GeoDataFrames to a PostgreSQL database.
Package: geopandas (pypi), vulnerable version: 1.1.1, fixed in: 1.1.2
Files changed by the fix:
geopandas/io/sql.py

Fix diff:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4588a0194c..d83adc4b8d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ Bug fixes:
   column (#3648).
 - Calling `del gdf["geometry"]` now will downcast to a `pd.DataFrame` if there are no geometry columns left
   in the dataframe (#3648).
+- Fix SQL injection in `to_postgis` via geometry column name (#3681).
 
 Community:
 
diff --git a/geopandas/io/sql.py b/geopandas/io/sql.py
index eb75b2bbc3..c11f63c7b4 100644
--- a/geopandas/io/sql.py
+++ b/geopandas/io/sql.py
@@ -431,7 +431,11 @@ def _write_postgis(
             # Only check SRID if table exists
             if connection.dialect.has_table(connection, name, schema):
                 target_srid = connection.execute(
-                    text(f"SELECT Find_SRID('{schema_name}', '{name}', '{geom_name}');")
+                    text(
+                        "SELECT Find_SRID(:schema_name, :name, :geom_name);"
+                    ).bindparams(
+                        schema_name=schema_name, name=name, geom_name=geom_name
+                    )
                 ).fetchone()[0]
 
                 if target_srid != srid:
diff --git a/geopandas/io/tests/test_sql.py b/geopandas/io/tests/test_sql.py
index 16c9a1db0d..748260ca59 100644
--- a/geopandas/io/tests/test_sql.py
+++ b/geopandas/io/tests/test_sql.py
@@ -6,6 +6,7 @@
 """
 
 import os
+import uuid
 import warnings
 from importlib.util import find_spec
 
@@ -841,3 +842,258 @@ def test_read_non_epsg_crs_chunksize(self, connection_postgis, df_nybb):
 
         validate_boro_df(df)
         assert df.crs == "ESRI:54052"
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_append_with_custom_geometry_column_name(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests that appending works correctly with custom geometry column names.
+        This ensures the SQL injection fix doesn't break normal functionality.
+        """
+        engine = engine_postgis
+        table = "test_custom_geom"
+
+        # Create GeoDataFrame with custom geometry column name
+        gdf = df_nybb.copy()
+        gdf = gdf.rename_geometry("custom_geom")
+
+        # Write initial data
+        write_postgis(gdf, con=engine, name=table, if_exists="replace")
+
+        # Append more data - this should work without SQL injection vulnerability
+        write_postgis(gdf, con=engine, name=table, if_exists="append")
+
+        # Verify data was appended correctly
+        sql = text(f'SELECT * FROM "{table}";')
+        df = read_postgis(sql, engine, geom_col="custom_geom")
+        assert len(df) == len(gdf) * 2
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_sql_injection_prevention_geometry_column(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests that SQL injection attempts via geometry column name are prevented.
+        This test verifies that malicious geometry column names are treated as
+        literal strings and not executed as SQL code.
+
+        This test is based on issue #3679 which reported SQL injection vulnerability
+        in the Find_SRID query when using to_postgis with if_exists='append'.
+        """
+        engine = engine_postgis
+        table = "test_sql_injection"
+
+        # Create a test table first to ensure append mode triggers
+        # the vulnerable code path
+        gdf_normal = df_nybb.copy()
+        write_postgis(gdf_normal, con=engine, name=table, if_exists="replace")
+
+        # Create a test table that would be targeted by SQL injection
+        # If SQL injection works, this table would be dropped
+        # Use random name to avoid conflicts with existing tables
+        test_target_table = f"test_target_{uuid.uuid4().hex[:12]}"
+        with engine.begin() as conn:
+            conn.execute(
+                text(f"CREATE TABLE IF NOT EXISTS {test_target_table} (id INTEGER);")
+            )
+            conn.execute(text(f"INSERT INTO {test_target_table} (id) VALUES (1);"))
+
+        # Create GeoDataFrame with malicious geometry column name
+        # This simulates an attacker trying to inject SQL via geometry column name
+        gdf_malicious = df_nybb.copy()
+        malicious_geom_name = f"geom'; DROP TABLE {test_target_table}; --"
+        gdf_malicious = gdf_malicious.rename_geometry(malicious_geom_name)
+
+        # First, verify both tables exist
+        sql_check = text(f"SELECT COUNT(*) FROM {table};")
+        sql_check_target = text(f"SELECT COUNT(*) FROM {test_target_table};")
+        with engine.connect() as conn:
+            initial_count = conn.execute(sql_check).fetchone()[0]
+            target_exists = conn.execute(sql_check_target).fetchone()[0] == 1
+
+        assert target_exists, "Target table should exist before SQL injection attempt"
+
+        # Attempt append - this should fail because the geometry column name
+        # doesn't match, but it should NOT execute the injected SQL
+        try:
+            write_postgis(gdf_malicious, con=engine, name=table, if_exists="append")
+            # If it doesn't raise an error, that's also fine - the important
+            # thing is that SQL injection didn't occur
+        except (ValueError, Exception):
+            # Expected - the geometry column name doesn't exist in the table
+            pass
+
+        # Verify both tables still exist and weren't dropped by SQL injection
+        with engine.connect() as conn:
+            final_count = conn.execute(sql_check).fetchone()[0]
+            target_still_exists = conn.execute(sql_check_target).fetchone()[0] == 1
+
+        assert final_count == initial_count, (
+            "Test table should still exist after SQL injection attempt"
+        )
+        assert target_still_exists, (
+            f"Target table '{test_target_table}' should not be dropped by SQL injection"
+        )
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_sql_injection_prevention_geometry_column_union(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests another SQL injection pattern: UNION SELECT attack
+        via geometry column name.
+        """
+        engine = engine_postgis
+        table = "test_sql_injection_union"
+
+        # Create initial table
+        gdf_normal = df_nybb.copy()
+        write_postgis(gdf_normal, con=engine, name=table, if_exists="replace")
+
+        # Create a test table that would be targeted by UNION SELECT injection
+        # Use random name to avoid conflicts with existing tables
+        test_target_table = f"test_target_{uuid.uuid4().hex[:12]}"
+        with engine.begin() as conn:
+            conn.execute(
+                text(f"CREATE TABLE IF NOT EXISTS {test_target_table} (password TEXT);")
+            )
+            conn.execute(
+                text(f"INSERT INTO {test_target_table} (password) VALUES ('secret');")
+            )
+
+        # Create GeoDataFrame with UNION-based SQL injection attempt
+        gdf_malicious = df_nybb.copy()
+        malicious_geom_name = (
+            f"geom') UNION SELECT password FROM {test_target_table} WHERE '1'='1"
+        )
+        gdf_malicious = gdf_malicious.rename_geometry(malicious_geom_name)
+
+        # Verify tables exist before injection attempt
+        sql_check = text(f"SELECT COUNT(*) FROM {table};")
+        sql_check_target = text(f"SELECT COUNT(*) FROM {test_target_table};")
+        with engine.connect() as conn:
+            initial_count = conn.execute(sql_check).fetchone()[0]
+            target_exists = conn.execute(sql_check_target).fetchone()[0] == 1
+
+        assert target_exists, "Target table should exist before SQL injection attempt"
+
+        # Attempt append - should not execute the UNION SELECT
+        try:
+            write_postgis(gdf_malicious, con=engine, name=table, if_exists="append")
+        except (ValueError, Exception):
+            # Expected - geometry column name mismatch
+            pass
+
+        # Verify table integrity maintained
+        with engine.connect() as conn:
+            final_count = conn.execute(sql_check).fetchone()[0]
+            target_still_exists = conn.execute(sql_check_target).fetchone()[0] == 1
+
+        assert final_count == initial_count, (
+            "Test table should still exist after SQL injection attempt"
+        )
+        assert target_still_exists, (
+            f"Target table '{test_target_table}' should not be "
+            "affected by SQL injection"
+        )
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_sql_injection_prevention_geometry_column_comment(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests SQL injection via comment syntax in geometry column name.
+        """
+        engine = engine_postgis
+        table = "test_sql_injection_comment"
+
+        # Create initial table
+        gdf_normal = df_nybb.copy()
+        write_postgis(gdf_normal, con=engine, name=table, if_exists="replace")
+
+        # Create GeoDataFrame with comment-based SQL injection
+        gdf_malicious = df_nybb.copy()
+        malicious_geom_name = "geom' -- DROP TABLE test_sql_injection_comment;"
+        gdf_malicious = gdf_malicious.rename_geometry(malicious_geom_name)
+
+        # Verify table exists
+        sql_check = text(f"SELECT COUNT(*) FROM {table};")
+        with engine.connect() as conn:
+            initial_count = conn.execute(sql_check).fetchone()[0]
+
+        # Attempt append
+        try:
+            write_postgis(gdf_malicious, con=engine, name=table, if_exists="append")
+        except (ValueError, Exception):
+            pass
+
+        # Verify table still exists
+        with engine.connect() as conn:
+            final_count = conn.execute(sql_check).fetchone()[0]
+            assert final_count == initial_count
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_sql_injection_prevention_geometry_column_semicolon(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests SQL injection via semicolon in geometry column name.
+        """
+        engine = engine_postgis
+        table = "test_sql_injection_semicolon"
+
+        # Create initial table
+        gdf_normal = df_nybb.copy()
+        write_postgis(gdf_normal, con=engine, name=table, if_exists="replace")
+
+        # Create GeoDataFrame with semicolon-based SQL injection
+        gdf_malicious = df_nybb.copy()
+        malicious_geom_name = "geom; DELETE FROM test_sql_injection_semicolon;"
+        gdf_malicious = gdf_malicious.rename_geometry(malicious_geom_name)
+
+        # Verify table exists
+        sql_check = text(f"SELECT COUNT(*) FROM {table};")
+        with engine.connect() as conn:
+            initial_count = conn.execute(sql_check).fetchone()[0]
+
+        # Attempt append
+        try:
+            write_postgis(gdf_malicious, con=engine, name=table, if_exists="append")
+        except (ValueError, Exception):
+            pass
+
+        # Verify table still exists and data is intact
+        with engine.connect() as conn:
+            final_count = conn.execute(sql_check).fetchone()[0]
+            assert final_count == initial_count
+
+    @pytest.mark.parametrize("engine_postgis", POSTGIS_DRIVERS, indirect=True)
+    def test_to_postgis_append_with_special_characters_in_geometry_column(
+        self, engine_postgis, df_nybb
+    ):
+        """
+        Tests that legitimate geometry column names with special characters
+        (but not SQL injection) still work correctly.
+        This ensures the fix doesn't break normal functionality with valid
+        but unusual column names.
+        """
+        engine = engine_postgis
+        table = "test_special_chars"
+
+        # Create GeoDataFrame with geometry column name containing special characters
+        # (but not SQL injection patterns)
+        gdf = df_nybb.copy()
+        # Use a valid but unusual geometry column name
+        gdf = gdf.rename_geometry("geom_with_underscores_123")
+
+        # Write initial data
+        write_postgis(gdf, con=engine, name=table, if_exists="replace")
+
+        # Append more data - should work correctly
+        write_postgis(gdf, con=engine, name=table, if_exists="append")
+
+        # Verify data was appended correctly
+        sql = text(f'SELECT * FROM "{table}";')
+        df = read_postgis(sql, engine, geom_col="geom_with_underscores_123")
+        assert len(df) == len(gdf) * 2