diff --git a/CVE-2025-6069-quad-complex-HTMLParser.patch b/CVE-2025-6069-quad-complex-HTMLParser.patch
new file mode 100644
index 0000000..c044f5f
--- /dev/null
+++ b/CVE-2025-6069-quad-complex-HTMLParser.patch
@@ -0,0 +1,187 @@
+From 9043edabc7e2f0dd655146e0a4571e2a0b2906af Mon Sep 17 00:00:00 2001
+From: Serhiy Storchaka <storchaka@gmail.com>
+Date: Fri, 13 Jun 2025 19:57:48 +0300
+Subject: [PATCH] gh-135462: Fix quadratic complexity in processing special
+ input in HTMLParser (GH-135464)
+
+End-of-file errors are now handled according to the HTML5 specs --
+comments and declarations are automatically closed, tags are ignored.
+(cherry picked from commit 6eb6c5dbfb528bd07d77b60fd71fd05d81d45c41)
+
+Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
+---
+ Lib/html/parser.py                                                       |   41 ++++++--
+ Lib/test/test_htmlparser.py                                              |   49 +++++++---
+ Misc/NEWS.d/next/Security/2025-06-13-15-55-22.gh-issue-135462.KBeJpc.rst |    4 
+ 3 files changed, 73 insertions(+), 21 deletions(-)
+ create mode 100644 Misc/NEWS.d/next/Security/2025-06-13-15-55-22.gh-issue-135462.KBeJpc.rst
+
+Index: Python-3.11.13/Lib/html/parser.py
+===================================================================
+--- Python-3.11.13.orig/Lib/html/parser.py	2025-07-02 17:11:09.096534277 +0200
++++ Python-3.11.13/Lib/html/parser.py	2025-07-02 17:11:16.977433541 +0200
+@@ -25,6 +25,7 @@
+ charref = re.compile('&#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]')
+ 
+ starttagopen = re.compile('<[a-zA-Z]')
++endtagopen = re.compile('</[a-zA-Z]')
+ piclose = re.compile('>')
+ commentclose = re.compile(r'--\s*>')
+ # Note:
+@@ -176,7 +177,7 @@
+                     k = self.parse_pi(i)
+                 elif startswith("<!", i):
+                     k = self.parse_html_declaration(i)
+-                elif (i + 1) < n:
++                elif (i + 1) < n or end:
+                     self.handle_data("<")
+                     k = i + 1
+                 else:
+@@ -184,17 +185,35 @@
+                 if k < 0:
+                     if not end:
+                         break
+-                    k = rawdata.find('>', i + 1)
+-                    if k < 0:
+-                        k = rawdata.find('<', i + 1)
+-                        if k < 0:
+-                            k = i + 1
++                    if starttagopen.match(rawdata, i):  # < + letter
++                        pass
++                    elif startswith("</", i):
++                        if i + 2 == n:
++                            self.handle_data("</")
++                        elif endtagopen.match(rawdata, i):  # </ + letter
++                            pass
++                        else:
++                            # bogus comment
++                            self.handle_comment(rawdata[i+2:])
++                    elif startswith("<!--", i):
++                        j = n
++                        for suffix in ("--!", "--", "-"):
++                            if rawdata.endswith(suffix, i+4):
++                                j -= len(suffix)
++                                break
++                        self.handle_comment(rawdata[i+4:j])
++                    elif startswith("<![CDATA[", i):
++                        self.unknown_decl(rawdata[i+3:])
++                    elif rawdata[i:i+9].lower() == '<!doctype':
++                        self.handle_decl(rawdata[i+2:])
++                    elif startswith("<!", i):
++                        # bogus comment
++                        self.handle_comment(rawdata[i+2:])
++                    elif startswith("<?", i):
++                        self.handle_pi(rawdata[i+2:])
+                     else:
+-                        k += 1
+-                    if self.convert_charrefs and not self.cdata_elem:
+-                        self.handle_data(unescape(rawdata[i:k]))
+-                    else:
+-                        self.handle_data(rawdata[i:k])
++                        raise AssertionError("we should not get here!")
++                    k = n
+                 i = self.updatepos(i, k)
+             elif startswith("&#", i):
+                 match = charref.match(rawdata, i)
+Index: Python-3.11.13/Lib/test/test_htmlparser.py
+===================================================================
+--- Python-3.11.13.orig/Lib/test/test_htmlparser.py	2025-07-02 17:11:10.487699349 +0200
++++ Python-3.11.13/Lib/test/test_htmlparser.py	2025-07-02 17:12:43.419502465 +0200
+@@ -4,6 +4,8 @@
+ import pprint
+ import unittest
+ 
++from test import support
++
+ 
+ class EventCollector(html.parser.HTMLParser):
+ 
+@@ -391,28 +393,34 @@
+                             ('data', '<'),
+                             ('starttag', 'bc<', [('a', None)]),
+                             ('endtag', 'html'),
+-                            ('data', '\n<img src="URL>'),
+-                            ('comment', '/img'),
+-                            ('endtag', 'html<')])
++                            ('data', '\n')])
+ 
+     def test_starttag_junk_chars(self):
++        self._run_check("<", [('data', '<')])
++        self._run_check("<>", [('data', '<>')])
++        self._run_check("< >", [('data', '< >')])
++        self._run_check("< ", [('data', '< ')])
+         self._run_check("</>", [])
++        self._run_check("<$>", [('data', '<$>')])
+         self._run_check("</$>", [('comment', '$')])
+         self._run_check("</", [('data', '</')])
+-        self._run_check("</a", [('data', '</a')])
++        self._run_check("</a", [])
++        self._run_check("</ a>", [('endtag', 'a')])
++        self._run_check("</ a", [('comment', ' a')])
+         self._run_check("<a<a>", [('starttag', 'a<a', [])])
+         self._run_check("</a<a>", [('endtag', 'a<a')])
+-        self._run_check("<!", [('data', '<!')])
+-        self._run_check("<a", [('data', '<a')])
+-        self._run_check("<a foo='bar'", [('data', "<a foo='bar'")])
+-        self._run_check("<a foo='bar", [('data', "<a foo='bar")])
+-        self._run_check("<a foo='>'", [('data', "<a foo='>'")])
+-        self._run_check("<a foo='>", [('data', "<a foo='>")])
++        self._run_check("<!", [('comment', '')])
++        self._run_check("<a", [])
++        self._run_check("<a foo='bar'", [])
++        self._run_check("<a foo='bar", [])
++        self._run_check("<a foo='>'", [])
++        self._run_check("<a foo='>", [])
+         self._run_check("<a$>", [('starttag', 'a$', [])])
+         self._run_check("<a$b>", [('starttag', 'a$b', [])])
+         self._run_check("<a$b/>", [('startendtag', 'a$b', [])])
+         self._run_check("<a$b  >", [('starttag', 'a$b', [])])
+         self._run_check("<a$b  />", [('startendtag', 'a$b', [])])
++        self._run_check("</a$b>", [('endtag', 'a$b')])
+ 
+     def test_slashes_in_starttag(self):
+         self._run_check('<a foo="var"/>', [('startendtag', 'a', [('foo', 'var')])])
+@@ -544,6 +552,7 @@
+                 '<!><!<-- this was an empty comment>'
+                 '<!!! another bogus comment !!!>')
+         expected = [
++            ('comment', 'ELEMENT br EMPTY'),
+             ('comment', ' not really a comment '),
+             ('comment', ' not a comment either --'),
+             ('comment', ' -- close enough --'),
+@@ -598,6 +607,26 @@
+              ('endtag', 'a'), ('data', ' bar & baz')]
+         )
+ 
++    @support.requires_resource('cpu')
++    def test_eof_no_quadratic_complexity(self):
++        # Each of these examples used to take about an hour.
++        # Now they take a fraction of a second.
++        def check(source):
++            parser = html.parser.HTMLParser()
++            parser.feed(source)
++            parser.close()
++        n = 120_000
++        check("<a " * n)
++        check("<a a=" * n)
++        check("</a " * 14 * n)
++        check("</a a=" * 11 * n)
++        check("<!--" * 4 * n)
++        check("<!" * 60 * n)
++        check("<?" * 19 * n)
++        check("</$" * 15 * n)
++        check("<![CDATA[" * 9 * n)
++        check("<!doctype" * 35 * n)
++
+ 
+ class AttributesTestCase(TestCaseBase):
+ 
+Index: Python-3.11.13/Misc/NEWS.d/next/Security/2025-06-13-15-55-22.gh-issue-135462.KBeJpc.rst
+===================================================================
+--- /dev/null	1970-01-01 00:00:00.000000000 +0000
++++ Python-3.11.13/Misc/NEWS.d/next/Security/2025-06-13-15-55-22.gh-issue-135462.KBeJpc.rst	2025-07-02 17:11:16.978605629 +0200
+@@ -0,0 +1,4 @@
++Fix quadratic complexity in processing specially crafted input in
++:class:`html.parser.HTMLParser`. End-of-file errors are now handled according
++to the HTML5 specs -- comments and declarations are automatically closed,
++tags are ignored.
diff --git a/python311.changes b/python311.changes
index 1f16727..a88d49b 100644
--- a/python311.changes
+++ b/python311.changes
@@ -1,3 +1,10 @@
+-------------------------------------------------------------------
+Wed Jul  2 14:47:20 UTC 2025 - Matej Cepl <mcepl@cepl.eu>
+
+- Add CVE-2025-6069-quad-complex-HTMLParser.patch to avoid worst
+  case quadratic complexity when processing certain crafted
+  malformed inputs with HTMLParser (CVE-2025-6069, bsc#1244705).
+
 -------------------------------------------------------------------
 Tue Jul  1 08:19:52 UTC 2025 - Daniel Garcia <daniel.garcia@suse.com>
 
diff --git a/python311.spec b/python311.spec
index 0a68887..13520fe 100644
--- a/python311.spec
+++ b/python311.spec
@@ -186,6 +186,9 @@ Patch19:        bso1227999-reproducible-builds.patch
 Patch22:        gh120226-fix-sendfile-test-kernel-610.patch
 # PATCH-FIX-UPSTREAM Add platform triplets for 64-bit LoongArch gh#python/cpython#30939 glaubitz@suse.com
 Patch24:        add-loongarch64-support.patch
+# PATCH-FIX-UPSTREAM CVE-2025-6069-quad-complex-HTMLParser.patch bsc#1244705 mcepl@suse.com
+# avoid quadratic complexity when processing malformed inputs with HTMLParser
+Patch25:        CVE-2025-6069-quad-complex-HTMLParser.patch
 BuildRequires:  autoconf-archive
 BuildRequires:  automake
 BuildRequires:  crypto-policies-scripts