diff --git a/changes/bug15823 b/changes/bug15823
new file mode 100644
index 000000000..987de5d9a
--- /dev/null
+++ b/changes/bug15823
@@ -0,0 +1,4 @@
+  o Minor bugfixes (hidden service):
+    - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells
+      on a client authorized hidden service. Fixes bug 15823; bugfix
+      on 0.2.1.6-alpha.
diff --git a/changes/bug17404 b/changes/bug17404
new file mode 100644
index 000000000..d524f6662
--- /dev/null
+++ b/changes/bug17404
@@ -0,0 +1,6 @@
+  o Major bugfixes (security, correctness):
+    - Fix a programming error that could cause us to read 4 bytes before
+      the beginning of an openssl string. This could be used to provoke
+      a crash on systems with an unusual malloc implementation, or
+      systems with unsual hardening installed. Fixes bug 17404; bugfix
+      on 0.2.3.6-alpha.
diff --git a/changes/bug18089 b/changes/bug18089
new file mode 100644
index 000000000..c1fb342f7
--- /dev/null
+++ b/changes/bug18089
@@ -0,0 +1,6 @@
+  o Minor fixes (security):
+    - Make memwipe() do nothing when passed a NULL pointer
+      or zero size. Check size argument to memwipe() for underflow.
+      Closes bug #18089. Reported by "gk", patch by "teor".
+      Bugfix on 0.2.3.25 and 0.2.4.6-alpha (#7352),
+      commit 49dd5ef3 on 7 Nov 2012.
diff --git a/src/common/crypto.c b/src/common/crypto.c
index 925beb352..522c1375c 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -2972,6 +2972,7 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret,
 /**
  * Destroy the <b>sz</b> bytes of data stored at <b>mem</b>, setting them to
  * the value <b>byte</b>.
+ * If <b>mem</b> is NULL or <b>sz</b> is zero, nothing happens.
  *
  * This function is preferable to memset, since many compilers will happily
  * optimize out memset() when they can convince themselves that the data being
@@ -2989,6 +2990,15 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret,
 void
 memwipe(void *mem, uint8_t byte, size_t sz)
 {
+  if (sz == 0) {
+    return;
+  }
+  /* If sz is nonzero, then mem must not be NULL. */
+  tor_assert(mem != NULL);
+
+  /* Data this large is likely to be an underflow. */
+  tor_assert(sz < SIZE_T_CEILING);
+
   /* Because whole-program-optimization exists, we may not be able to just
    * have this function call "memset".  A smart compiler could inline it, then
    * eliminate dead memsets, and declare itself to be clever. */
diff --git a/src/common/tortls.c b/src/common/tortls.c
index 4222f6dbf..840b677cb 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -2676,6 +2676,10 @@ dn_indicates_v3_cert(X509_NAME *name)
   len = ASN1_STRING_to_UTF8(&s, str);
   if (len < 0)
     return 0;
+  if (len < 4) {
+    OPENSSL_free(s);
+    return 1;
+  }
   r = fast_memneq(s + len - 4, ".net", 4);
   OPENSSL_free(s);
   return r;
diff --git a/src/or/rendservice.c b/src/or/rendservice.c
index 436f2f4b6..0a5456739 100644
--- a/src/or/rendservice.c
+++ b/src/or/rendservice.c
@@ -939,11 +939,13 @@ rend_service_requires_uptime(rend_service_t *service)
   return 0;
 }
 
-/** Check client authorization of a given <b>descriptor_cookie</b> for
- * <b>service</b>. Return 1 for success and 0 for failure. */
+/** Check client authorization of a given <b>descriptor_cookie</b> of
+ * length <b>cookie_len</b> for <b>service</b>. Return 1 for success
+ * and 0 for failure. */
 static int
 rend_check_authorization(rend_service_t *service,
-                         const char *descriptor_cookie)
+                         const char *descriptor_cookie,
+                         size_t cookie_len)
 {
   rend_authorized_client_t *auth_client = NULL;
   tor_assert(service);
@@ -954,6 +956,13 @@ rend_check_authorization(rend_service_t *service,
     return 0;
   }
 
+  if (cookie_len != REND_DESC_COOKIE_LEN) {
+    log_info(LD_REND, "Descriptor cookie is %lu bytes, but we expected "
+                      "%lu bytes. Dropping cell.",
+             (unsigned long)cookie_len, (unsigned long)REND_DESC_COOKIE_LEN);
+    return 0;
+  }
+
   /* Look up client authorization by descriptor cookie. */
   SMARTLIST_FOREACH(service->clients, rend_authorized_client_t *, client, {
     if (tor_memeq(client->descriptor_cookie, descriptor_cookie,
@@ -1300,7 +1309,8 @@ rend_service_introduce(origin_circuit_t *circuit, const uint8_t *request,
   if (service->clients) {
     if (parsed_req->version == 3 && parsed_req->u.v3.auth_len > 0) {
       if (rend_check_authorization(service,
-                                   (const char*)parsed_req->u.v3.auth_data)) {
+                                   (const char*)parsed_req->u.v3.auth_data,
+                                   parsed_req->u.v3.auth_len)) {
         log_info(LD_REND, "Authorization data in INTRODUCE2 cell are valid.");
       } else {
         log_info(LD_REND, "The authorization data that are contained in "