diff --git a/nrs/ext/bzlib/bzlib.c b/nrs/ext/bzlib/bzlib.c
index fef83b2..1b37d7a 100644
--- a/nrs/ext/bzlib/bzlib.c
+++ b/nrs/ext/bzlib/bzlib.c
@@ -115,7 +115,7 @@ Int32 NSISCALL BZ2_indexIntoF ( Int32 indx, Int32 *cftab )
 
 
 static
-void NSISCALL unRLE_obuf_to_output_SMALL ( DState* s )
+Bool NSISCALL unRLE_obuf_to_output_SMALL ( DState* s )
 {
    UChar k1;
   while (True) {
@@ -130,7 +130,11 @@ void NSISCALL unRLE_obuf_to_output_SMALL ( DState* s )
      }
 
      /* can a new run be started? */
-     if (s->nblock_used == s->save.nblock+1) return;
+     if (s->nblock_used == s->save.nblock+1) return False;
+
+     /* Only caused by corrupt data stream? */
+     if (s->nblock_used > s->save_nblock+1)
+         return True;
 
      s->state_out_len = 1;
      s->state_out_ch = s->k0;
@@ -154,7 +158,7 @@ void NSISCALL unRLE_obuf_to_output_SMALL ( DState* s )
   }
 }
 #else//!small, fast
-static void NSISCALL unRLE_obuf_to_output_FAST ( DState* s )
+static Bool NSISCALL unRLE_obuf_to_output_FAST ( DState* s )
 {
    UChar k1;
 
@@ -195,6 +199,10 @@ static void NSISCALL unRLE_obuf_to_output_FAST ( DState* s )
                cs_avail_out--;
             }
          }
+         /* Only caused by corrupt data stream? */
+         if (c_nblock_used > s_save_nblockPP)
+             return True;
+
          /* can a new run be started? */
          if (c_nblock_used == s_save_nblockPP) {
             c_state_out_len = 0; goto return_notr;
@@ -231,6 +239,7 @@ static void NSISCALL unRLE_obuf_to_output_FAST ( DState* s )
       s->next_out     = (unsigned char*) cs_next_out;
       s->avail_out    = cs_avail_out;
       /* end save */
+      return False;
 }
 
 #endif
@@ -239,14 +248,16 @@ static void NSISCALL unRLE_obuf_to_output_FAST ( DState* s )
 /*---------------------------------------------------*/
 int NSISCALL BZ2_bzDecompress( DState *s )
 {
+   Bool    corrupt;
    while (True) {
       if (s->state == BZ_X_IDLE) return BZ_SEQUENCE_ERROR;
       if (s->state == BZ_X_OUTPUT) {
 #ifdef NSIS_COMPRESS_BZIP2_SMALLMODE
-        unRLE_obuf_to_output_SMALL ( s );
+        corrupt = unRLE_obuf_to_output_SMALL ( s );
 #else
-        unRLE_obuf_to_output_FAST ( s );
+        corrupt = unRLE_obuf_to_output_FAST ( s );
 #endif
+         if (corrupt) return BZ_DATA_ERROR;
          if (s->nblock_used == s->save.nblock+1 && s->state_out_len == 0) {
             s->state = BZ_X_BLKHDR_1;
          } else {
diff --git a/nrs/ext/bzlib/bzlib.h b/nrs/ext/bzlib/bzlib.h
index 69aeaad..23cb394 100644
--- a/nrs/ext/bzlib/bzlib.h
+++ b/nrs/ext/bzlib/bzlib.h
@@ -266,11 +266,13 @@ typedef struct {
 /*-- Macros for decompression. --*/
 
 #define BZ_GET_FAST(cccc)                     \
+    if (s->tPos >= (UInt32)100000 * NSIS_COMPRESS_BZIP2_LEVEL) return True; \
     s->tPos = s->tt[s->tPos];                 \
     cccc = (UChar)(s->tPos & 0xff);           \
     s->tPos >>= 8;
 
 #define BZ_GET_FAST_C(cccc)                   \
+    if (c_tPos >= (UInt32)100000 * NSIS_COMPRESS_BZIP2_LEVEL) return True; \
     c_tPos = c_tt[c_tPos];                    \
     cccc = (UChar)(c_tPos & 0xff);            \
     c_tPos >>= 8;
@@ -296,6 +298,7 @@ typedef struct {
    (((UInt32)s->ll16[i]) | (GET_LL4(i) << 16))
 
 #define BZ_GET_SMALL(cccc)                            \
+      if (s->tPos >= (UInt32)100000 * NSIS_COMPRESS_BZIP2_LEVEL) return True; \
       cccc = BZ2_indexIntoF ( s->tPos, s->cftab );    \
       s->tPos = GET_LL(s->tPos);
 
diff --git a/nrs/ext/bzlib/decompress.c b/nrs/ext/bzlib/decompress.c
index 33c890a..2a942a6 100644
--- a/nrs/ext/bzlib/decompress.c
+++ b/nrs/ext/bzlib/decompress.c
@@ -1,14 +1,14 @@
 /*
  * This file is a part of the bzip2 compression module for NSIS.
- * 
+ *
  * Copyright and license information can be found below.
  * Modifications Copyright (C) 1999-2015 Nullsoft and Contributors
- * 
+ *
  * The original zlib source code is available at
  * http://www.bzip.org/
- * 
+ *
  * This modification is not compatible with the original bzip2.
- * 
+ *
  * This software is provided 'as-is', without any express or implied
  * warranty.
  *
@@ -252,8 +252,14 @@ Int32 NSISCALL BZ2_decompress ( DState* s )
             j++;
             if (j >= nGroups) RETURN(BZ_DATA_ERROR);
          }
-         s->selectorMtf[i] = j;
+         /* Having more than BZ_MAX_SELECTORS doesn't make much sense
+            since they will never be used, but some implementations might
+            "round up" the number of selectors, so just ignore those. */
+         if (i < BZ_MAX_SELECTORS)
+           s->selectorMtf[i] = j;
       }
+      if (nSelectors > BZ_MAX_SELECTORS)
+        nSelectors = BZ_MAX_SELECTORS;
 
       /*--- Undo the MTF values for the selectors. ---*/
       {
@@ -337,6 +343,13 @@ Int32 NSISCALL BZ2_decompress ( DState* s )
             N = 1;
             while (nextSym == BZ_RUNA || nextSym == BZ_RUNB)
             {
+               /* Check that N doesn't get too big, so that es doesn't
+               go negative.  The maximum value that can be
+               RUNA/RUNB encoded is equal to the block size (post
+               the initial RLE), viz, 900k, so bounding N at 2
+               million should guard against overflow without
+               rejecting any legitimate inputs. */
+               if (N >= 2*1024*1024) RETURN(BZ_DATA_ERROR);
                if (nextSym == BZ_RUNA) es += N;
                N = N << 1;
                if (nextSym == BZ_RUNB) es += N;
@@ -446,10 +459,28 @@ Int32 NSISCALL BZ2_decompress ( DState* s )
       s->state_out_ch  = 0;
       s->state = BZ_X_OUTPUT;
 
-      /*-- Set up cftab to facilitate generation of T^(-1) --*/
+      /* Check: unzftab entries in range. */
+      for (i = 0; i <= 255; i++) {
+         if (s->unzftab[i] < 0 || s->unzftab[i] > nblock)
+            RETURN(BZ_DATA_ERROR);
+      }
+      /* Actually generate cftab. */
       s->cftab[0] = 0;
+      /* Actually generate cftab. */
       for (i = 1; i <= 256; i++) s->cftab[i] = s->unzftab[i-1]+s->cftab[i-1];
-//      for (i = 1; i <= 256; i++) s->cftab[i] += s->cftab[i-1];
+      /* Check: cftab entries in range. */
+      for (i = 0; i <= 256; i++) {
+         if (s->cftab[i] < 0 || s->cftab[i] > nblock) {
+            /* s->cftab[i] can legitimately be == nblock */
+            RETURN(BZ_DATA_ERROR);
+         }
+      }
+      /* Check: cftab entries non-descending. */
+      for (i = 1; i <= 256; i++) {
+         if (s->cftab[i-1] > s->cftab[i]) {
+            RETURN(BZ_DATA_ERROR);
+         }
+      }
 
 #ifdef NSIS_COMPRESS_BZIP2_SMALLMODE
       {