diff --git a/usr.bin/compress/zopen.c b/usr.bin/compress/zopen.c
index 68d41dc3c2a9..0d3f178d1643 100644
--- a/usr.bin/compress/zopen.c
+++ b/usr.bin/compress/zopen.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: zopen.c,v 1.14 2011/08/16 03:24:47 christos Exp $	*/
+/*	$NetBSD: zopen.c,v 1.15 2011/08/16 13:55:01 joerg Exp $	*/
 
 /*-
  * Copyright (c) 1985, 1986, 1992, 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)zopen.c	8.1 (Berkeley) 6/27/93";
 #else
-static char rcsid[] = "$NetBSD: zopen.c,v 1.14 2011/08/16 03:24:47 christos Exp $";
+static char rcsid[] = "$NetBSD: zopen.c,v 1.15 2011/08/16 13:55:01 joerg Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -486,7 +486,7 @@ zread(void *cookie, char *rbp, int num)
 	block_compress = maxbits & BLOCK_MASK;
 	maxbits &= BIT_MASK;
 	maxmaxcode = 1L << maxbits;
-	if (maxbits > BITS) {
+	if (maxbits > BITS || maxbits < 12) {
 		errno = EFTYPE;
 		return (-1);
 	}
@@ -497,14 +497,7 @@ zread(void *cookie, char *rbp, int num)
 		tab_suffixof(code) = (char_type) code;
 	}
 	free_ent = block_compress ? FIRST : 256;
-
-	finchar = oldcode = getcode(zs);
-	if (oldcode == -1)	/* EOF already? */
-		return (0);	/* Get out of here */
-
-	/* First code must be 8 bits = char. */
-	*bp++ = (u_char)finchar;
-	count--;
+	oldcode = -1;
 	stackp = de_stack;
 
 	while ((code = getcode(zs)) > -1) {
@@ -513,24 +506,31 @@ zread(void *cookie, char *rbp, int num)
 			for (code = 255; code >= 0; code--)
 				tab_prefixof(code) = 0;
 			clear_flg = 1;
-			free_ent = FIRST - 1;
-			if ((code = getcode(zs)) == -1)	/* O, untimely death! */
-				break;
+			free_ent = FIRST;
+			oldcode = -1;
+			continue;
 		}
 		incode = code;
 
-		/* Special case FOR kWkWk string. */
+		/* Special case for kWkWk string. */
 		if (code >= free_ent) {
+			if (code > free_ent || oldcode == -1) {
+				/* Bad stream. */
+				errno = EINVAL;
+				return (-1);
+			}
 			*stackp++ = finchar;
 			code = oldcode;
 		}
+		/*
+		 * The above condition ensures that code < free_ent.
+		 * The construction of tab_prefixof in turn guarantees that
+		 * each iteration decreases code and therefore stack usage is
+		 * bound by 1 << BITS - 256.
+		 */
 
 		/* Generate output characters in reverse order. */
 		while (code >= 256) {
-			if (stackp - de_stack >= HSIZE - 1) {
-				errno = EOVERFLOW;
-				return -1;
-			}
 			*stackp++ = tab_suffixof(code);
 			code = tab_prefixof(code);
 		}
@@ -544,7 +544,7 @@ middle:		do {
 		} while (stackp > de_stack);
 
 		/* Generate the new entry. */
-		if ((code = free_ent) < maxmaxcode) {
+		if ((code = free_ent) < maxmaxcode && oldcode != -1) {
 			tab_prefixof(code) = (u_short) oldcode;
 			tab_suffixof(code) = finchar;
 			free_ent = code + 1;
diff --git a/usr.bin/gzip/zuncompress.c b/usr.bin/gzip/zuncompress.c
index 74da4a6f2143..11b57ed76118 100644
--- a/usr.bin/gzip/zuncompress.c
+++ b/usr.bin/gzip/zuncompress.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: zuncompress.c,v 1.10 2011/08/16 03:25:34 christos Exp $ */
+/*	$NetBSD: zuncompress.c,v 1.11 2011/08/16 13:55:02 joerg Exp $ */
 
 /*-
  * Copyright (c) 1985, 1986, 1992, 1993
@@ -246,7 +246,7 @@ zread(void *cookie, char *rbp, int num)
 	zs->zs_block_compress = zs->zs_maxbits & BLOCK_MASK;
 	zs->zs_maxbits &= BIT_MASK;
 	zs->zs_maxmaxcode = 1L << zs->zs_maxbits;
-	if (zs->zs_maxbits > BITS) {
+	if (zs->zs_maxbits > BITS || zs->zs_maxbits < 12) {
 		errno = EFTYPE;
 		return (-1);
 	}
@@ -258,13 +258,7 @@ zread(void *cookie, char *rbp, int num)
 	}
 	zs->zs_free_ent = zs->zs_block_compress ? FIRST : 256;
 
-	zs->u.r.zs_finchar = zs->u.r.zs_oldcode = getcode(zs);
-	if (zs->u.r.zs_oldcode == -1)	/* EOF already? */
-		return (0);	/* Get out of here */
-
-	/* First code must be 8 bits = char. */
-	*bp++ = (u_char)zs->u.r.zs_finchar;
-	count--;
+	zs->u.r.zs_oldcode = -1;
 	zs->u.r.zs_stackp = de_stack;
 
 	while ((zs->u.r.zs_code = getcode(zs)) > -1) {
@@ -274,24 +268,32 @@ zread(void *cookie, char *rbp, int num)
 			    zs->u.r.zs_code--)
 				tab_prefixof(zs->u.r.zs_code) = 0;
 			zs->zs_clear_flg = 1;
-			zs->zs_free_ent = FIRST - 1;
-			if ((zs->u.r.zs_code = getcode(zs)) == -1)	/* O, untimely death! */
-				break;
+			zs->zs_free_ent = FIRST;
+			zs->u.r.zs_oldcode = -1;
+			continue;
 		}
 		zs->u.r.zs_incode = zs->u.r.zs_code;
 
 		/* Special case for KwKwK string. */
 		if (zs->u.r.zs_code >= zs->zs_free_ent) {
+			if (zs->u.r.zs_code > zs->zs_free_ent ||
+			    zs->u.r.zs_oldcode == -1) {
+				/* Bad stream. */
+				errno = EINVAL;
+				return (-1);
+			}
 			*zs->u.r.zs_stackp++ = zs->u.r.zs_finchar;
 			zs->u.r.zs_code = zs->u.r.zs_oldcode;
 		}
+		/*
+		 * The above condition ensures that code < free_ent.
+		 * The construction of tab_prefixof in turn guarantees that
+		 * each iteration decreases code and therefore stack usage is
+		 * bound by 1 << BITS - 256.
+		 */
 
 		/* Generate output characters in reverse order. */
 		while (zs->u.r.zs_code >= 256) {
-			if (zs->u.r.zs_stackp - de_stack >= HSIZE - 1) {
-				errno = EOVERFLOW;
-				return -1;
-			}
 			*zs->u.r.zs_stackp++ = tab_suffixof(zs->u.r.zs_code);
 			zs->u.r.zs_code = tab_prefixof(zs->u.r.zs_code);
 		}
@@ -305,7 +307,8 @@ middle:		do {
 		} while (zs->u.r.zs_stackp > de_stack);
 
 		/* Generate the new entry. */
-		if ((zs->u.r.zs_code = zs->zs_free_ent) < zs->zs_maxmaxcode) {
+		if ((zs->u.r.zs_code = zs->zs_free_ent) < zs->zs_maxmaxcode &&
+		    zs->u.r.zs_oldcode != -1) {
 			tab_prefixof(zs->u.r.zs_code) = (u_short) zs->u.r.zs_oldcode;
 			tab_suffixof(zs->u.r.zs_code) = zs->u.r.zs_finchar;
 			zs->zs_free_ent = zs->u.r.zs_code + 1;