ecpg: Fix out-of-bound writes due to processing of invalid bytea data

ECPG assumes that any bytea data it receives from a backend starts with
'\x' as its first two bytes, but a check was missed to enforce that.  A
rogue server sending some garbage bytea data would be able to crash a
client, resulting in a client-side DoS, in the most common cases.

Reported-by: ylwangtju <ylwangtju@qq.com>
Backpatch-through: 14
Security: CVE-2026-16241

src/interfaces/ecpg/ecpglib/data.c

@@ -526,6 +526,13 @@ ecpg_get_data(const PGresult *results, int act_tuple, int act_field, int lineno,
 									src_size,
 									dec_size;
 
+						if (size < 2 || pval[0] != '\\' || pval[1] != 'x')
+						{
+							ecpg_raise(lineno, ECPG_BYTEA_FORMAT,
+									   ECPG_SQLSTATE_DATATYPE_MISMATCH, pval);
+							return false;
+						}
+
 						dst_size = ecpg_hex_enc_len(varcharsize);
 						src_size = size - 2;	/* exclude backslash + 'x' */
 						dec_size = src_size < dst_size ? src_size : dst_size;

src/interfaces/ecpg/ecpglib/error.c

@@ -130,6 +130,13 @@ ecpg_raise(int line, int code, const char *sqlstate, const char *str)
 					 ecpg_gettext("inserting an array of variables is not supported on line %d"), line);
 			break;
 
+		case ECPG_BYTEA_FORMAT:
+			snprintf(sqlca->sqlerrm.sqlerrmc, sizeof(sqlca->sqlerrm.sqlerrmc),
+			/*------
+			   translator: this string will be truncated at 149 characters expanded.  */
+					 ecpg_gettext("invalid input syntax for type bytea: \"%s\", on line %d"), str, line);
+			break;
+
 		case ECPG_NO_CONN:
 			snprintf(sqlca->sqlerrm.sqlerrmc, sizeof(sqlca->sqlerrm.sqlerrmc),
 			/*------

src/interfaces/ecpg/include/ecpgerrno.h

@@ -32,6 +32,7 @@
 #define ECPG_NO_ARRAY			-214
 #define ECPG_DATA_NOT_ARRAY		-215
 #define ECPG_ARRAY_INSERT		-216
+#define ECPG_BYTEA_FORMAT		-217
 
 #define ECPG_NO_CONN			-220
 #define ECPG_NOT_CONN			-221

src/interfaces/ecpg/test/expected/sql-bytea.c

@@ -356,17 +356,36 @@ if (sqlca.sqlcode < 0) sqlprint();}
 if (sqlca.sqlcode < 0) sqlprint();}
 #line 115 "bytea.pgc"
 
-	{ ECPGtrans(__LINE__, NULL, "commit");
-#line 116 "bytea.pgc"
+
+	/* Test for invalid bytea format */
+	{ ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select '' :: text", ECPGt_EOIT, 
+	ECPGt_bytea,&(recv_buf[0]),(long)DATA_SIZE,(long)1,sizeof(struct bytea_2), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 118 "bytea.pgc"
 
 if (sqlca.sqlcode < 0) sqlprint();}
-#line 116 "bytea.pgc"
+#line 118 "bytea.pgc"
+
+	{ ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select '\\\\a1234' :: text", ECPGt_EOIT, 
+	ECPGt_bytea,&(recv_buf[0]),(long)DATA_SIZE,(long)1,sizeof(struct bytea_2), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 119 "bytea.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 119 "bytea.pgc"
+
+
+	{ ECPGtrans(__LINE__, NULL, "commit");
+#line 121 "bytea.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 121 "bytea.pgc"
 
 	{ ECPGdisconnect(__LINE__, "CURRENT");
-#line 117 "bytea.pgc"
+#line 122 "bytea.pgc"
 
 if (sqlca.sqlcode < 0) sqlprint();}
-#line 117 "bytea.pgc"
+#line 122 "bytea.pgc"
 
 
 	return 0;

src/interfaces/ecpg/test/expected/sql-bytea.stderr

@@ -181,7 +181,29 @@ SQL error: invalid statement name "cursor1" on line 82
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_process_output on line 115: OK: DROP TABLE
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ECPGtrans on line 116: action "commit"; connection "ecpg1_regression"
+[NO_PID]: ecpg_execute on line 118: query: select '' :: text; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 118: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 118: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 118: RESULT:  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlcode -217 on line 118: invalid input syntax for type bytea: "", on line 118
+[NO_PID]: sqlca: code: -217, state: 42804
+SQL error: invalid input syntax for type bytea: "", on line 118
+[NO_PID]: ecpg_execute on line 119: query: select '\\a1234' :: text; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 119: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 119: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 119: RESULT: \\a1234 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlcode -217 on line 119: invalid input syntax for type bytea: "\\a1234", on line 119
+[NO_PID]: sqlca: code: -217, state: 42804
+SQL error: invalid input syntax for type bytea: "\\a1234", on line 119
+[NO_PID]: ECPGtrans on line 121: action "commit"; connection "ecpg1_regression"
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: deallocate_one on line 0: name sel_stmt
 [NO_PID]: sqlca: code: 0, state: 00000

src/interfaces/ecpg/test/sql/bytea.pgc

@@ -113,6 +113,11 @@ while (0)
 	dump_binary(recv_short_buf.arr, recv_short_buf.len, ind[1]);
 
 	exec sql drop table test;
+
+	/* Test for invalid bytea format */
+	exec sql select ''::text into :recv_buf[0];
+	exec sql select '\\a1234'::text into :recv_buf[0];
+
 	exec sql commit;
 	exec sql disconnect;