diff --git a/src/lj_cparse.c b/src/lj_cparse.c
index 70b82af3..a393965e 100644
--- a/src/lj_cparse.c
+++ b/src/lj_cparse.c
@@ -169,7 +169,8 @@ static CPToken cp_number(CPState *cp)
   TValue o;
   do { cp_save(cp, cp->c); } while (lj_char_isident(cp_get(cp)));
   cp_save(cp, '\0');
-  fmt = lj_strscan_scan((const uint8_t *)sbufB(&cp->sb), &o, STRSCAN_OPT_C);
+  fmt = lj_strscan_scan((const uint8_t *)sbufB(&cp->sb), sbuflen(&cp->sb)-1,
+			&o, STRSCAN_OPT_C);
   if (fmt == STRSCAN_INT) cp->val.id = CTID_INT32;
   else if (fmt == STRSCAN_U32) cp->val.id = CTID_UINT32;
   else if (!(cp->mode & CPARSE_MODE_SKIP))
diff --git a/src/lj_lex.c b/src/lj_lex.c
index 05a2efc3..ada0876e 100644
--- a/src/lj_lex.c
+++ b/src/lj_lex.c
@@ -105,7 +105,7 @@ static void lex_number(LexState *ls, TValue *tv)
     lex_savenext(ls);
   }
   lex_save(ls, '\0');
-  fmt = lj_strscan_scan((const uint8_t *)sbufB(&ls->sb), tv,
+  fmt = lj_strscan_scan((const uint8_t *)sbufB(&ls->sb), sbuflen(&ls->sb)-1, tv,
 	  (LJ_DUALNUM ? STRSCAN_OPT_TOINT : STRSCAN_OPT_TONUM) |
 	  (LJ_HASFFI ? (STRSCAN_OPT_LL|STRSCAN_OPT_IMAG) : 0));
   if (LJ_DUALNUM && fmt == STRSCAN_INT) {
diff --git a/src/lj_strscan.c b/src/lj_strscan.c
index 948c84a7..433b33a3 100644
--- a/src/lj_strscan.c
+++ b/src/lj_strscan.c
@@ -370,9 +370,11 @@ static StrScanFmt strscan_bin(const uint8_t *p, TValue *o,
 }
 
 /* Scan string containing a number. Returns format. Returns value in o. */
-StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
+StrScanFmt lj_strscan_scan(const uint8_t *p, MSize len, TValue *o,
+			   uint32_t opt)
 {
   int32_t neg = 0;
+  const uint8_t *pe = p + len;
 
   /* Remove leading space, parse sign and non-numbers. */
   if (LJ_UNLIKELY(!lj_char_isdigit(*p))) {
@@ -390,7 +392,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
 	p += 3;
       }
       while (lj_char_isspace(*p)) p++;
-      if (*p) return STRSCAN_ERROR;
+      if (*p || p < pe) return STRSCAN_ERROR;
       o->u64 = tmp.u64;
       return STRSCAN_NUM;
     }
@@ -488,6 +490,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
       while (lj_char_isspace(*p)) p++;
       if (*p) return STRSCAN_ERROR;
     }
+    if (p < pe) return STRSCAN_ERROR;
 
     /* Fast path for decimal 32 bit integers. */
     if (fmt == STRSCAN_INT && base == 10 &&
@@ -523,7 +526,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
 
 int LJ_FASTCALL lj_strscan_num(GCstr *str, TValue *o)
 {
-  StrScanFmt fmt = lj_strscan_scan((const uint8_t *)strdata(str), o,
+  StrScanFmt fmt = lj_strscan_scan((const uint8_t *)strdata(str), str->len, o,
 				   STRSCAN_OPT_TONUM);
   lua_assert(fmt == STRSCAN_ERROR || fmt == STRSCAN_NUM);
   return (fmt != STRSCAN_ERROR);
@@ -532,7 +535,7 @@ int LJ_FASTCALL lj_strscan_num(GCstr *str, TValue *o)
 #if LJ_DUALNUM
 int LJ_FASTCALL lj_strscan_number(GCstr *str, TValue *o)
 {
-  StrScanFmt fmt = lj_strscan_scan((const uint8_t *)strdata(str), o,
+  StrScanFmt fmt = lj_strscan_scan((const uint8_t *)strdata(str), str->len, o,
 				   STRSCAN_OPT_TOINT);
   lua_assert(fmt == STRSCAN_ERROR || fmt == STRSCAN_NUM || fmt == STRSCAN_INT);
   if (fmt == STRSCAN_INT) setitype(o, LJ_TISNUM);
diff --git a/src/lj_strscan.h b/src/lj_strscan.h
index 42aa1455..30e271b2 100644
--- a/src/lj_strscan.h
+++ b/src/lj_strscan.h
@@ -22,7 +22,8 @@ typedef enum {
   STRSCAN_INT, STRSCAN_U32, STRSCAN_I64, STRSCAN_U64,
 } StrScanFmt;
 
-LJ_FUNC StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt);
+LJ_FUNC StrScanFmt lj_strscan_scan(const uint8_t *p, MSize len, TValue *o,
+				   uint32_t opt);
 LJ_FUNC int LJ_FASTCALL lj_strscan_num(GCstr *str, TValue *o);
 #if LJ_DUALNUM
 LJ_FUNC int LJ_FASTCALL lj_strscan_number(GCstr *str, TValue *o);