diff --git a/src/h2.c b/src/h2.c
index f034e3d..f35abc1 100644
--- a/src/h2.c
+++ b/src/h2.c
@@ -45,6 +45,23 @@
 	 [H2_FT_CONTINUATION ] = { .dir = 3, .min_id = 1, .max_id = H2_MAX_STREAM_ID, .min_len = 0, .max_len = H2_MAX_FRAME_LEN, },
 };
 
+/* Looks into <ist> for forbidden characters for header values (0x00, 0x0A,
+ * 0x0D), starting at pointer <start> which must be within <ist>. Returns
+ * non-zero if such a character is found, 0 otherwise. When run on unlikely
+ * header match, it's recommended to first check for the presence of control
+ * chars using ist_find_ctl().
+ */
+static int has_forbidden_char(const struct ist ist, const char *start)
+{
+	do {
+		if ((uint8_t)*start <= 0x0d &&
+		    (1U << (uint8_t)*start) & ((1<<13) | (1<<10) | (1<<0)))
+			return 1;
+		start++;
+	} while (start < ist.ptr + ist.len);
+	return 0;
+}
+
 /* Parse the Content-Length header field of an HTTP/2 request. The function
  * checks all possible occurrences of a comma-delimited value, and verifies
  * if any of them doesn't match a previous value. It returns <0 if a value
@@ -309,6 +326,7 @@
 	uint32_t used = htx_used_space(htx);
 	struct htx_sl *sl = NULL;
 	unsigned int sl_flags = 0;
+	const char *ctl;
 
 	lck = ck = -1; // no cookie for now
 	fields = 0;
@@ -327,6 +345,13 @@
 			phdr = h2_str_to_phdr(list[idx].n);
 		}
 
+		/* RFC7540#10.3: intermediaries forwarding to HTTP/1 must take care of
+		 * rejecting NUL, CR and LF characters.
+		 */
+		ctl = ist_find_ctl(list[idx].v);
+		if (unlikely(ctl) && has_forbidden_char(list[idx].v, ctl))
+			goto fail;
+
 		if (phdr > 0 && phdr < H2_PHDR_NUM_ENTRIES) {
 			/* insert a pseudo header by its index (in phdr) and value (in value) */
 			if (fields & ((1 << phdr) | H2_PHDR_FND_NONE)) {
@@ -553,6 +578,7 @@
 	uint32_t used = htx_used_space(htx);
 	struct htx_sl *sl = NULL;
 	unsigned int sl_flags = 0;
+	const char *ctl;
 
 	fields = 0;
 	for (idx = 0; list[idx].n.len != 0; idx++) {
@@ -570,6 +596,13 @@
 			phdr = h2_str_to_phdr(list[idx].n);
 		}
 
+		/* RFC7540#10.3: intermediaries forwarding to HTTP/1 must take care of
+		 * rejecting NUL, CR and LF characters.
+		 */
+		ctl = ist_find_ctl(list[idx].v);
+		if (unlikely(ctl) && has_forbidden_char(list[idx].v, ctl))
+			goto fail;
+
 		if (phdr > 0 && phdr < H2_PHDR_NUM_ENTRIES) {
 			/* insert a pseudo header by its index (in phdr) and value (in value) */
 			if (fields & ((1 << phdr) | H2_PHDR_FND_NONE)) {
@@ -675,6 +708,7 @@
  */
 int h2_make_htx_trailers(struct http_hdr *list, struct htx *htx)
 {
+	const char *ctl;
 	uint32_t idx;
 	int i;
 
@@ -705,6 +739,13 @@
 		    isteq(list[idx].n, ist("transfer-encoding")))
 			goto fail;
 
+		/* RFC7540#10.3: intermediaries forwarding to HTTP/1 must take care of
+		 * rejecting NUL, CR and LF characters.
+		 */
+		ctl = ist_find_ctl(list[idx].v);
+		if (unlikely(ctl) && has_forbidden_char(list[idx].v, ctl))
+			goto fail;
+
 		if (!htx_add_trailer(htx, list[idx].n, list[idx].v))
 			goto fail;
 	}