diff --git a/ssh/deattack.c b/ssh/deattack.c
index b307073..faf6ab1 100644
--- a/ssh/deattack.c
+++ b/ssh/deattack.c
@@ -93,13 +93,17 @@ check_crc(u_char *S, u_char *buf, u_int32_t len)
 	return crc == 0;
 }
 
+void
+deattack_init(struct deattack_ctx *dctx)
+{
+	bzero(dctx, sizeof(*dctx));
+	dctx->n = HASH_MINSIZE / HASH_ENTRYSIZE;
+}
 
 /* Detect a crc32 compensation attack on a packet */
 int
-detect_attack(u_char *buf, u_int32_t len)
+detect_attack(struct deattack_ctx *dctx, u_char *buf, u_int32_t len)
 {
-	static u_int16_t *h = NULL;
-	static u_int32_t n = HASH_MINSIZE / HASH_ENTRYSIZE;
 	u_int16_t *tmp;
 	u_int32_t i, j, l, same;
 	u_char *c, *d;
@@ -107,21 +111,23 @@ detect_attack(u_char *buf, u_int32_t len)
 	if (len > (SSH_MAXBLOCKS * SSH_BLOCKSIZE) ||
 	    len % SSH_BLOCKSIZE != 0)
 		return DEATTACK_ERROR;
-	for (l = n; l < HASH_FACTOR(len / SSH_BLOCKSIZE); l = l << 2)
+	for (l = dctx->n; l < HASH_FACTOR(len / SSH_BLOCKSIZE); l = l << 2)
 		;
 
-	if (h == NULL) {
-		if ((h = calloc(l, HASH_ENTRYSIZE)) == NULL)
+	if (dctx->h == NULL) {
+		if ((dctx->h = calloc(l, HASH_ENTRYSIZE)) == NULL)
 			return DEATTACK_ERROR;
-		n = l;
+		dctx->n = l;
 	} else {
-		if (l > n) {
-			if ((tmp = reallocn(h, l, HASH_ENTRYSIZE)) == NULL) {
-				free(h);
+		if (l > dctx->n) {
+			if ((tmp = reallocn(dctx->h, l,
+			    HASH_ENTRYSIZE)) == NULL) {
+				free(dctx->h);
+				dctx->h = NULL;
 				return DEATTACK_ERROR;
 			}
-			h = tmp;
-			n = l;
+			dctx->h = tmp;
+			dctx->n = l;
 		}
 	}
 
@@ -138,12 +144,12 @@ detect_attack(u_char *buf, u_int32_t len)
 		}
 		return DEATTACK_OK;
 	}
-	memset(h, HASH_UNUSEDCHAR, n * HASH_ENTRYSIZE);
+	memset(dctx->h, HASH_UNUSEDCHAR, dctx->n * HASH_ENTRYSIZE);
 
 	for (c = buf, same = j = 0; c < (buf + len); c += SSH_BLOCKSIZE, j++) {
-		for (i = HASH(c) & (n - 1); h[i] != HASH_UNUSED;
-		    i = (i + 1) & (n - 1)) {
-			if (!CMP(c, buf + h[i] * SSH_BLOCKSIZE)) {
+		for (i = HASH(c) & (dctx->n - 1); dctx->h[i] != HASH_UNUSED;
+		    i = (i + 1) & (dctx->n - 1)) {
+			if (!CMP(c, buf + dctx->h[i] * SSH_BLOCKSIZE)) {
 				if (++same > MAX_IDENTICAL)
 					return DEATTACK_DOS_DETECTED;
 				if (check_crc(c, buf, len))
@@ -152,7 +158,7 @@ detect_attack(u_char *buf, u_int32_t len)
 					break;
 			}
 		}
-		h[i] = j;
+		dctx->h[i] = j;
 	}
 	return DEATTACK_OK;
 }
diff --git a/ssh/deattack.h b/ssh/deattack.h
index a29c550..d46b50f 100644
--- a/ssh/deattack.h
+++ b/ssh/deattack.h
@@ -28,5 +28,11 @@
 #define DEATTACK_DOS_DETECTED	2
 #define DEATTACK_ERROR		3
 
-int	 detect_attack(u_char *, u_int32_t);
+struct deattack_ctx {
+	u_int16_t *h;
+	u_int32_t n;
+};
+
+void	 deattack_init(struct deattack_ctx *);
+int	 detect_attack(struct deattack_ctx *, u_char *, u_int32_t);
 #endif
diff --git a/ssh/packet.c b/ssh/packet.c
index 5bcc643..0777053 100644
--- a/ssh/packet.c
+++ b/ssh/packet.c
@@ -198,6 +198,9 @@ struct session_state {
 	/* One-off warning about weak ciphers */
 	int cipher_warning_done;
 
+	/* SSH1 CRC compensation attack detector */
+	struct deattack_ctx deattack;
+
 	TAILQ_HEAD(, packet) outgoing;
 };
 
@@ -279,7 +282,7 @@ ssh_packet_set_connection(struct ssh *ssh, int fd_in, int fd_out)
 	    (const u_char *)"", 0, NULL, 0, CIPHER_DECRYPT)) != 0)
 		fatal("%s: cipher_init failed: %s", __func__, ssh_err(r));
 	state->newkeys[MODE_IN] = state->newkeys[MODE_OUT] = NULL;
-
+	deattack_init(&state->deattack);
 	return ssh;
 }
 
@@ -1486,8 +1489,8 @@ ssh_packet_read_poll1(struct ssh *ssh, u_char *typep)
 	 * Ariel Futoransky(futo@core-sdi.com)
 	 */
 	if (!state->receive_context.plaintext) {
-		switch (detect_attack(sshbuf_ptr(state->input),
-		    padded_len)) {
+		switch (detect_attack(&state->deattack,
+		    sshbuf_ptr(state->input), padded_len)) {
 		case DEATTACK_OK:
 			break;
 		case DEATTACK_DETECTED:
@@ -1498,8 +1501,7 @@ ssh_packet_read_poll1(struct ssh *ssh, u_char *typep)
 			ssh_packet_disconnect(ssh,
 			    "deattack denial of service detected");
 		default:
-			ssh_packet_disconnect(ssh,
-			    "deattack error");
+			ssh_packet_disconnect(ssh, "deattack error");
 		}
 	}