diff --git a/libxml2-2.12.5-extra-content-parser-error.patch b/libxml2-2.12.5-extra-content-parser-error.patch
new file mode 100644
index 0000000..fed6fcb
--- /dev/null
+++ b/libxml2-2.12.5-extra-content-parser-error.patch
@@ -0,0 +1,84 @@
+From 9bb32f5a7db09951187a608d7ba1b71b41127da0 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Tue, 2 Jan 2024 17:52:43 +0100
+Subject: [PATCH] parser: Fix buffer size checks
+
+Don't test size of remaining data. This causes false positives with
+memory buffers.
+
+Also impose XML_MAX_HUGE_LENGTH limit when parsing with XML_PARSE_HUGE.
+---
+ parser.c          | 15 ++++++++++-----
+ parserInternals.c | 14 ++++++++------
+ 2 files changed, 18 insertions(+), 11 deletions(-)
+
+diff --git a/parser.c b/parser.c
+index 845e0fd3..77106c1d 100644
+--- a/parser.c
++++ b/parser.c
+@@ -12198,6 +12198,8 @@ encoding_error:
+ int
+ xmlParseChunk(xmlParserCtxtPtr ctxt, const char *chunk, int size,
+               int terminate) {
++    size_t curBase;
++    size_t maxLength;
+     int end_in_lf = 0;
+ 
+     if (ctxt == NULL)
+@@ -12236,13 +12238,16 @@ xmlParseChunk(xmlParserCtxtPtr ctxt, const char *chunk, int size,
+     if (ctxt->instate == XML_PARSER_EOF)
+         return(ctxt->errNo);
+ 
+-    if ((ctxt->input != NULL) &&
+-         (((ctxt->input->end - ctxt->input->cur) > XML_MAX_LOOKUP_LIMIT) ||
+-         ((ctxt->input->cur - ctxt->input->base) > XML_MAX_LOOKUP_LIMIT)) &&
+-        ((ctxt->options & XML_PARSE_HUGE) == 0)) {
+-        xmlFatalErr(ctxt, XML_ERR_INTERNAL_ERROR, "Huge input lookup");
++    curBase = ctxt->input->cur - ctxt->input->base;
++    maxLength = (ctxt->options & XML_PARSE_HUGE) ?
++                XML_MAX_HUGE_LENGTH :
++                XML_MAX_LOOKUP_LIMIT;
++    if (curBase > maxLength) {
++        xmlFatalErr(ctxt, XML_ERR_INTERNAL_ERROR,
++                    "Buffer size limit exceeded, try XML_PARSE_HUGE\n");
+         xmlHaltParser(ctxt);
+     }
++
+     if ((ctxt->errNo != XML_ERR_OK) && (ctxt->disableSAX == 1))
+         return(ctxt->errNo);
+ 
+diff --git a/parserInternals.c b/parserInternals.c
+index 166397bd..9484ebdd 100644
+--- a/parserInternals.c
++++ b/parserInternals.c
+@@ -511,8 +511,11 @@ int
+ xmlParserGrow(xmlParserCtxtPtr ctxt) {
+     xmlParserInputPtr in = ctxt->input;
+     xmlParserInputBufferPtr buf = in->buf;
+-    ptrdiff_t curEnd = in->end - in->cur;
+-    ptrdiff_t curBase = in->cur - in->base;
++    size_t curEnd = in->end - in->cur;
++    size_t curBase = in->cur - in->base;
++    size_t maxLength = (ctxt->options & XML_PARSE_HUGE) ?
++                       XML_MAX_HUGE_LENGTH :
++                       XML_MAX_LOOKUP_LIMIT;
+     int ret;
+ 
+     if (buf == NULL)
+@@ -526,10 +529,9 @@ xmlParserGrow(xmlParserCtxtPtr ctxt) {
+     if (buf->error != 0)
+         return(-1);
+ 
+-    if (((curEnd > XML_MAX_LOOKUP_LIMIT) ||
+-         (curBase > XML_MAX_LOOKUP_LIMIT)) &&
+-        ((ctxt->options & XML_PARSE_HUGE) == 0)) {
+-        xmlErrMemory(ctxt, "Huge input lookup");
++    if (curBase > maxLength) {
++        xmlFatalErr(ctxt, XML_ERR_INTERNAL_ERROR,
++                    "Buffer size limit exceeded, try XML_PARSE_HUGE\n");
+         xmlHaltParser(ctxt);
+ 	return(-1);
+     }
+-- 
+2.54.0
+
diff --git a/libxml2.spec b/libxml2.spec
index 669c5a7..26260d5 100644
--- a/libxml2.spec
+++ b/libxml2.spec
@@ -1,6 +1,6 @@
 Name:           libxml2
 Version:        2.12.5
-Release:        11%{?dist}
+Release:        12%{?dist}
 Summary:        Library providing XML and HTML support
 
 # list.c, dict.c and few others use ISC-Veillard
@@ -41,6 +41,9 @@ Patch10:        libxml2-2.12.5-CVE-2025-32414.patch
 Patch11:        libxml2-2.12.5-xmllint-error-code.patch
 # https://redhat.atlassian.net/browse/RHEL-36782
 Patch12:        libxml2-2.12.5-CVE-2024-34459.patch
+# https://gitlab.gnome.org/GNOME/libxml2/-/commit/85f99023ae2eaec94ae0799fd37281a7f234d99a.patch
+# https://redhat.atlassian.net/browse/RHEL-126803
+Patch13:        libxml2-2.12.5-extra-content-parser-error.patch
 
 BuildRequires:  cmake-rpm-macros
 BuildRequires:  gcc
@@ -181,6 +184,9 @@ popd
 %{python3_sitelib}/__pycache__/drv_libxml2.*
 
 %changelog
+* Sat May 30 2026 David King <dking@redhat.com> - 2.12.5-12
+- Fix parser error (RHEL-126803)
+
 * Mon May 18 2026 David King <dking@redhat.com> - 2.12.5-11
 - Fix CVE-2024-34459 (RHEL-36782)