diff --git a/lib/decompress_unlzo.c b/lib/decompress_unlzo.c
index 855d9d3..7eb3b80 100644
--- a/lib/decompress_unlzo.c
+++ b/lib/decompress_unlzo.c
@@ -48,14 +48,25 @@
 
 #define LZO_BLOCK_SIZE        (256*1024l)
 #define HEADER_HAS_FILTER      0x00000800L
+#define HEADER_SIZE_MIN       (9 + 7     + 4 + 8     + 1       + 4)
+#define HEADER_SIZE_MAX       (9 + 7 + 1 + 8 + 8 + 4 + 1 + 255 + 4)
 
-STATIC inline int INIT parse_header(u8 *input, u8 *skip)
+STATIC inline int INIT parse_header(u8 *input, int *skip, int in_len)
 {
 	int l;
 	u8 *parse = input;
+	u8 *end = input + in_len;
 	u8 level = 0;
 	u16 version;
 
+	/*
+	 * Check that there's enough input to possibly have a valid header.
+	 * Then it is possible to parse several fields until the minimum
+	 * size may have been used.
+	 */
+	if (in_len < HEADER_SIZE_MIN)
+		return 0;
+
 	/* read magic: 9 first bits */
 	for (l = 0; l < 9; l++) {
 		if (*parse++ != lzop_magic[l])
@@ -73,6 +84,15 @@
 	else
 		parse += 4; /* flags */
 
+	/*
+	 * At least mode, mtime_low, filename length, and checksum must
+	 * be left to be parsed. If also mtime_high is present, it's OK
+	 * because the next input buffer check is after reading the
+	 * filename length.
+	 */
+	if (end - parse < 8 + 1 + 4)
+		return 0;
+
 	/* skip mode and mtime_low */
 	parse += 8;
 	if (version >= 0x0940)
@@ -80,6 +100,8 @@
 
 	l = *parse++;
 	/* don't care about the file name, and skip checksum */
+	if (end - parse < l + 4)
+		return 0;
 	parse += l + 4;
 
 	*skip = parse - input;
@@ -92,7 +114,8 @@
 				u8 *output, int *posp,
 				void (*error) (char *x))
 {
-	u8 skip = 0, r = 0;
+	u8 r = 0;
+	int skip = 0;
 	u32 src_len, dst_len;
 	size_t tmp;
 	u8 *in_buf, *in_buf_save, *out_buf;
@@ -134,19 +157,25 @@
 	if (fill)
 		fill(in_buf, lzo1x_worst_compress(LZO_BLOCK_SIZE));
 
-	if (!parse_header(input, &skip)) {
+	if (!parse_header(input, &skip, in_len)) {
 		error("invalid header");
 		goto exit_2;
 	}
 	in_buf += skip;
+	in_len -= skip;
 
 	if (posp)
 		*posp = skip;
 
 	for (;;) {
 		/* read uncompressed block size */
+		if (in_len < 4) {
+			error("file corrupted");
+			goto exit_2;
+		}
 		dst_len = get_unaligned_be32(in_buf);
 		in_buf += 4;
+		in_len -= 4;
 
 		/* exit if last block */
 		if (dst_len == 0) {
@@ -161,10 +190,15 @@
 		}
 
 		/* read compressed block size, and skip block checksum info */
+		if (in_len < 8) {
+			error("file corrupted");
+			goto exit_2;
+		}
 		src_len = get_unaligned_be32(in_buf);
 		in_buf += 8;
+		in_len -= 8;
 
-		if (src_len <= 0 || src_len > dst_len) {
+		if (src_len <= 0 || src_len > dst_len || src_len > in_len) {
 			error("file corrupted");
 			goto exit_2;
 		}
@@ -196,8 +230,10 @@
 		if (fill) {
 			in_buf = in_buf_save;
 			fill(in_buf, lzo1x_worst_compress(LZO_BLOCK_SIZE));
-		} else
+		} else {
 			in_buf += src_len;
+			in_len -= src_len;
+		}
 	}
 
 	ret = 0;