[OE-core][scarthgap][PATCH] python3: fix CVE-2026-15308

["Deepak Rathore -X (deeratho - E INFOCHIPS PRIVATE LIMITED at Cisco)" <deeratho@cisco.com>]

From: Deepak Rathore <deeratho@cisco.com>

Backport the upstream CPython fix for CVE-2026-15308 to Python
3.12.13. The issue is a CPU denial of service in incremental
html.parser.HTMLParser parsing, where repeated feed() calls with
unterminated markup could repeatedly rescan and concatenate a growing
buffer.

The embedded patch is based on the Python 3.13 backport in [1]. The
public CVE advisory is referenced in [2]. Scarthgap-specific source
differences are recorded under Backport Changes in the embedded patch
header.

[1] https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced
[2] https://nvd.nist.gov/vuln/detail/CVE-2026-15308

Signed-off-by: Deepak Rathore <deeratho@cisco.com>
---
 .../python/python3/CVE-2026-15308.patch       | 116 ++++++++++++++++++
 .../python/python3_3.12.13.bb                 |   1 +
 2 files changed, 117 insertions(+)
 create mode 100644 meta/recipes-devtools/python/python3/CVE-2026-15308.patch

diff --git a/meta/recipes-devtools/python/python3/CVE-2026-15308.patch b/meta/recipes-devtools/python/python3/CVE-2026-15308.patch
new file mode 100644
index 0000000000..7ed63b17ce
--- /dev/null
+++ b/meta/recipes-devtools/python/python3/CVE-2026-15308.patch
@@ -0,0 +1,116 @@
+From b30795b2ecf621df2c09b059b9fa7d881f537378 Mon Sep 17 00:00:00 2001
+From: "Miss Islington (bot)"
+ <31488909+miss-islington@users.noreply.github.com>
+Date: Sat, 4 Jul 2026 20:01:22 +0200
+Subject: [PATCH] [3.13] gh-153030: Fix quadratic complexity in incremental
+ parsing in HTMLParser (GH-153031) (GH-153040)
+
+When an unterminated construct (e.g. a tag or comment) spanned many
+feed() calls, rescanning the growing buffer and concatenating new data
+onto it were both quadratic.  New data is now accumulated in a list and
+only joined and parsed once enough has piled up.
+
+CVE: CVE-2026-15308
+Upstream-Status: Backport [https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced]
+
+Backport Changes:
+- Omitted Misc/NEWS.d/next/Security/2026-07-04-17-00-00.gh-issue-153030.RovkP6.rst
+  because the target source does not carry pending NEWS fragments.
+
+(cherry picked from commit bcf98ddbc40ec9b3ee87da0124a5660b19b7e606)
+Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
+Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
+(cherry picked from commit 7933f4bf7131aa4140750f9404f5de0aa2969ced)
+Signed-off-by: Deepak Rathore <deeratho@cisco.com>
+
+---
+ Lib/html/parser.py          | 32 ++++++++++++++++++++++++++++++--
+ Lib/test/test_htmlparser.py | 20 ++++++++++++++++++++
+ 2 files changed, 50 insertions(+), 2 deletions(-)
+
+diff --git a/Lib/html/parser.py b/Lib/html/parser.py
+index bfab3e64cd5..c5d2340b712 100644
+--- a/Lib/html/parser.py
++++ b/Lib/html/parser.py
+@@ -138,6 +138,9 @@ class HTMLParser(_markupbase.ParserBase):
+         self.cdata_elem = None
+         self._support_cdata = True
+         self._escapable = True
++        self._pending = []
++        self._pending_len = 0
++        self._parse_threshold = 1
+         super().reset()
+
+     def feed(self, data):
+@@ -146,11 +149,36 @@ class HTMLParser(_markupbase.ParserBase):
+         Call this as often as you want, with as little or as much text
+         as you want (may include '\n').
+         """
+-        self.rawdata = self.rawdata + data
+-        self.goahead(0)
++        # Accumulate new data in a list and only join and parse it once
++        # enough has piled up.  Rescanning an unparsed buffer (e.g. an
++        # unterminated tag) and concatenating onto it on every call would
++        # both be quadratic in the input size.
++        self._pending_len += len(data)
++        if self._pending_len < self._parse_threshold:
++            self._pending.append(data)
++        else:
++            if not self._pending:
++                self.rawdata += data
++            else:
++                self._pending.append(data)
++                self.rawdata += ''.join(self._pending)
++                self._pending.clear()
++            self._pending_len = 0
++            n = len(self.rawdata)
++            self.goahead(0)
++            if len(self.rawdata) < n:
++                # Some data was parsed; resume on the next call.
++                self._parse_threshold = 1
++            else:
++                # Nothing was parsed; wait until the buffer doubles.
++                self._parse_threshold = len(self.rawdata)
+
+     def close(self):
+         """Handle any buffered data."""
++        if self._pending:
++            self.rawdata += ''.join(self._pending)
++            self._pending.clear()
++            self._pending_len = 0
+         self.goahead(1)
+
+     __starttag_text = None
+diff --git a/Lib/test/test_htmlparser.py b/Lib/test/test_htmlparser.py
+index 303c0baa87b..e6d92a7ec51 100644
+--- a/Lib/test/test_htmlparser.py
++++ b/Lib/test/test_htmlparser.py
+@@ -930,6 +930,26 @@ text
+         check("<![CDATA[" * 9 * n)
+         check("<!doctype" * 35 * n)
+
++    @support.requires_resource('cpu')
++    def test_incremental_no_quadratic_complexity(self):
++        # An unterminated construct fed in many small chunks used to take
++        # quadratic time, both to rescan and to concatenate the buffer.
++        # Now it takes a fraction of a second.
++        def check(prefix, chunk, suffix):
++            parser = html.parser.HTMLParser()
++            parser.feed(prefix)
++            for _ in range(200_000):
++                parser.feed(chunk)
++            parser.feed(suffix)
++            parser.close()
++        chunk = "a" * 64
++        check("<!--", chunk, "-->")       # comment
++        check("<?", chunk, ">")           # processing instruction
++        check("<!doctype ", chunk, ">")   # doctype
++        check("<![CDATA[", chunk, "]]>")  # CDATA section
++        check("<a href='", chunk, "'>")   # start tag
++        check("<script>", chunk, "</script>")  # RAWTEXT element
++
+
+ class AttributesTestCase(TestCaseBase):
+
+--
+2.51.0
diff --git a/meta/recipes-devtools/python/python3_3.12.13.bb b/meta/recipes-devtools/python/python3_3.12.13.bb
index de174f7bfd..a3d07d14a4 100644
--- a/meta/recipes-devtools/python/python3_3.12.13.bb
+++ b/meta/recipes-devtools/python/python3_3.12.13.bb
@@ -47,6 +47,7 @@ SRC_URI = "http://www.python.org/ftp/python/${PV}/Python-${PV}.tar.xz \
            file://CVE-2026-11940.patch \
            file://CVE-2026-11972.patch \
            file://CVE-2026-9669.patch \
+           file://CVE-2026-15308.patch \
            "
 
 SRC_URI:append:class-native = " \
-- 
2.35.6