diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f8fb27be1..a06371373d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # 1.8.5 / unreleased
 
+## Security Notes
+
+[MRI] Pulled in upstream patches from libxml2 that address CVE-2018-14404 and CVE-2018-14567. Full details are available in #1785. Note that these patches are not yet (as of 2018-08-15) in an upstream release of libxml2.
+
+
 ## Bug fixes
 
 * [MRI] Fix regression in installation when building against system libraries, where some systems would not be able to find libxml2 or libxslt when present. (Regression introduced in v1.8.3.) [#1722]
diff --git a/Manifest.txt b/Manifest.txt
index aa62f20966..7e8b83ef7c 100644
--- a/Manifest.txt
+++ b/Manifest.txt
@@ -251,6 +251,8 @@ lib/xercesImpl.jar
 lib/xml-apis.jar
 lib/xsd/xmlparser/nokogiri.rb
 patches/libxml2/0001-Revert-Do-not-URI-escape-in-server-side-includes.patch
+patches/libxml2/0002-Fix-nullptr-deref-with-XPath-logic-ops.patch
+patches/libxml2/0003-Fix-infinite-loop-in-LZMA-decompression.patch
 patches/sort-patches-by-date
 suppressions/README.txt
 suppressions/nokogiri_ruby-2.supp
diff --git a/patches/libxml2/0002-Fix-nullptr-deref-with-XPath-logic-ops.patch b/patches/libxml2/0002-Fix-nullptr-deref-with-XPath-logic-ops.patch
new file mode 100644
index 0000000000..1345c0c8ce
--- /dev/null
+++ b/patches/libxml2/0002-Fix-nullptr-deref-with-XPath-logic-ops.patch
@@ -0,0 +1,54 @@
+From a436374994c47b12d5de1b8b1d191a098fa23594 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Mon, 30 Jul 2018 12:54:38 +0200
+Subject: [PATCH] Fix nullptr deref with XPath logic ops
+
+If the XPath stack is corrupted, for example by a misbehaving extension
+function, the "and" and "or" XPath operators could dereference NULL
+pointers. Check that the XPath stack isn't empty and optimize the
+logic operators slightly.
+
+Closes: https://gitlab.gnome.org/GNOME/libxml2/issues/5
+
+Also see
+https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=901817
+https://bugzilla.redhat.com/show_bug.cgi?id=1595985
+
+This is CVE-2018-14404.
+
+Thanks to Guy Inbar for the report.
+---
+ xpath.c | 10 ++++------
+ 1 file changed, 4 insertions(+), 6 deletions(-)
+
+diff --git a/xpath.c b/xpath.c
+index 3fae0bf..5e3bb9f 100644
+--- a/xpath.c
++++ b/xpath.c
+@@ -13234,9 +13234,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
+ 		return(0);
+ 	    }
+             xmlXPathBooleanFunction(ctxt, 1);
+-            arg1 = valuePop(ctxt);
+-            arg1->boolval &= arg2->boolval;
+-            valuePush(ctxt, arg1);
++            if (ctxt->value != NULL)
++                ctxt->value->boolval &= arg2->boolval;
+ 	    xmlXPathReleaseObject(ctxt->context, arg2);
+             return (total);
+         case XPATH_OP_OR:
+@@ -13252,9 +13251,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
+ 		return(0);
+ 	    }
+             xmlXPathBooleanFunction(ctxt, 1);
+-            arg1 = valuePop(ctxt);
+-            arg1->boolval |= arg2->boolval;
+-            valuePush(ctxt, arg1);
++            if (ctxt->value != NULL)
++                ctxt->value->boolval |= arg2->boolval;
+ 	    xmlXPathReleaseObject(ctxt->context, arg2);
+             return (total);
+         case XPATH_OP_EQUAL:
+-- 
+2.17.1
+
diff --git a/patches/libxml2/0003-Fix-infinite-loop-in-LZMA-decompression.patch b/patches/libxml2/0003-Fix-infinite-loop-in-LZMA-decompression.patch
new file mode 100644
index 0000000000..e5a4ce8b7e
--- /dev/null
+++ b/patches/libxml2/0003-Fix-infinite-loop-in-LZMA-decompression.patch
@@ -0,0 +1,50 @@
+From 2240fbf5912054af025fb6e01e26375100275e74 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Mon, 30 Jul 2018 13:14:11 +0200
+Subject: [PATCH] Fix infinite loop in LZMA decompression
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Check the liblzma error code more thoroughly to avoid infinite loops.
+
+Closes: https://gitlab.gnome.org/GNOME/libxml2/issues/13
+Closes: https://bugzilla.gnome.org/show_bug.cgi?id=794914
+
+This is CVE-2018-9251 and CVE-2018-14567.
+
+Thanks to Dongliang Mu and Simon Wörner for the reports.
+---
+ xzlib.c | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+diff --git a/xzlib.c b/xzlib.c
+index a839169..0ba88cf 100644
+--- a/xzlib.c
++++ b/xzlib.c
+@@ -562,6 +562,10 @@ xz_decomp(xz_statep state)
+                          "internal error: inflate stream corrupt");
+                 return -1;
+             }
++            /*
++             * FIXME: Remapping a couple of error codes and falling through
++             * to the LZMA error handling looks fragile.
++             */
+             if (ret == Z_MEM_ERROR)
+                 ret = LZMA_MEM_ERROR;
+             if (ret == Z_DATA_ERROR)
+@@ -587,6 +591,11 @@ xz_decomp(xz_statep state)
+             xz_error(state, LZMA_PROG_ERROR, "compression error");
+             return -1;
+         }
++        if ((state->how != GZIP) &&
++            (ret != LZMA_OK) && (ret != LZMA_STREAM_END)) {
++            xz_error(state, ret, "lzma error");
++            return -1;
++        }
+     } while (strm->avail_out && ret != LZMA_STREAM_END);
+ 
+     /* update available output and crc check value */
+-- 
+2.17.1
+