diff --git a/changes/bug21018 b/changes/bug21018
new file mode 100644
index 000000000..49a8b47a2
--- /dev/null
+++ b/changes/bug21018
@@ -0,0 +1,11 @@
+  o Major bugfixes (parsing, security):
+
+    - Fix a bug in parsing that could cause clients to read a single
+      byte past the end of an allocated region. This bug could be
+      used to cause hardened clients (built with
+      --enable-expensive-hardening) to crash if they tried to visit
+      a hostile hidden service.  Non-hardened clients are only
+      affected depending on the details of their platform's memory
+      allocator. Fixes bug 21018; bugfix on 0.2.0.8-alpha. Found by
+      using libFuzzer. Also tracked as TROVE-2016-12-002 and as
+      CVE-2016-1254.
diff --git a/src/or/rendcommon.c b/src/or/rendcommon.c
index d1f8b1af9..296df5566 100644
--- a/src/or/rendcommon.c
+++ b/src/or/rendcommon.c
@@ -1327,8 +1327,10 @@ rend_cache_store_v2_desc_as_client(const char *desc,
                                                     intro_size);
     if (n_intro_points <= 0) {
       log_warn(LD_REND, "Failed to parse introduction points. Either the "
-               "service has published a corrupt descriptor or you have "
-               "provided invalid authorization data.");
+               "service has published a corrupt descriptor, or you have "
+               "provided invalid authorization data, or (maybe!) the "
+               "server is deliberately serving broken data in an attempt "
+               "to crash you with bug 21018.");
       retval = -2;
       goto err;
     } else if (n_intro_points > MAX_INTRO_POINTS) {
diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index 176c16f90..71373ce63 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -3857,7 +3857,7 @@ get_next_token(memarea_t *area,
 
   if (tok->tp == ERR_) {
     /* No keyword matched; call it an "K_opt" or "A_unrecognized" */
-    if (**s == '@')
+    if (*s < eol && **s == '@')
       tok->tp = A_UNKNOWN_;
     else
       tok->tp = K_OPT;
@@ -4863,7 +4863,7 @@ rend_decrypt_introduction_points(char **ipos_decrypted,
         crypto_cipher_free(cipher);
 
         len = ipos_encrypted_size - 2 - client_entries_len - CIPHER_IV_LEN;
-        dec = tor_malloc(len);
+        dec = tor_malloc_zero(len + 1);
         declen = crypto_cipher_decrypt_with_iv(session_key, dec, len,
             ipos_encrypted + 2 + client_entries_len,
             ipos_encrypted_size - 2 - client_entries_len);
@@ -4895,7 +4895,7 @@ rend_decrypt_introduction_points(char **ipos_decrypted,
                         "small.");
       return -1;
     }
-    dec = tor_malloc_zero(ipos_encrypted_size - CIPHER_IV_LEN - 1);
+    dec = tor_malloc_zero(ipos_encrypted_size - CIPHER_IV_LEN - 1 + 1);
 
     declen = crypto_cipher_decrypt_with_iv(descriptor_cookie, dec,
                                            ipos_encrypted_size -