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Add CVE-2024-6923-follow-up-EOL-email-headers.patch

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It is a follow-up to the previous fix of CVE-2024-6923 further encoding
EOL possibly hidden in email headers (bsc#1257181).
This commit is contained in:
Matej Cepl
2026-01-27 17:58:02 +01:00
parent 8b786ccb53
commit 6230bce579
3 changed files with 117 additions and 0 deletions
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105
CVE-2024-6923-follow-up-EOL-email-headers.patch Normal file
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@@ -0,0 +1,105 @@
From 7ef18bbf2f92550e65547c0a55995c423e237944 Mon Sep 17 00:00:00 2001
From: Seth Michael Larson <seth@python.org>
Date: Fri, 23 Jan 2026 08:59:35 -0600
Subject: [PATCH] gh-144125: email: verify headers are sound in BytesGenerator
(cherry picked from commit 052e55e7d44718fe46cbba0ca995cb8fcc359413)
Co-authored-by: Seth Michael Larson <seth@python.org>
Co-authored-by: Denis Ledoux <dle@odoo.com>
Co-authored-by: Denis Ledoux <5822488+beledouxdenis@users.noreply.github.com>
Co-authored-by: Petr Viktorin <302922+encukou@users.noreply.github.com>
Co-authored-by: Bas Bloemsaat <1586868+basbloemsaat@users.noreply.github.com>
---
Lib/email/generator.py | 12 +++++++++++-
Lib/test/test_email/test_generator.py | 4 +++-
Lib/test/test_email/test_policy.py | 6 +++++-
.../2026-01-21-12-34-05.gh-issue-144125.TAz5uo.rst | 4 ++++
4 files changed, 23 insertions(+), 3 deletions(-)
create mode 100644 Misc/NEWS.d/next/Security/2026-01-21-12-34-05.gh-issue-144125.TAz5uo.rst
diff --git a/Lib/email/generator.py b/Lib/email/generator.py
index ce94f5c56fe34e..a03eb1fbbc9288 100644
--- a/Lib/email/generator.py
+++ b/Lib/email/generator.py
@@ -22,6 +22,7 @@
NLCRE = re.compile(r'\r\n|\r|\n')
fcre = re.compile(r'^From ', re.MULTILINE)
NEWLINE_WITHOUT_FWSP = re.compile(r'\r\n[^ \t]|\r[^ \n\t]|\n[^ \t]')
+NEWLINE_WITHOUT_FWSP_BYTES = re.compile(br'\r\n[^ \t]|\r[^ \n\t]|\n[^ \t]')
class Generator:
@@ -429,7 +430,16 @@ def _write_headers(self, msg):
# This is almost the same as the string version, except for handling
# strings with 8bit bytes.
for h, v in msg.raw_items():
- self._fp.write(self.policy.fold_binary(h, v))
+ folded = self.policy.fold_binary(h, v)
+ if self.policy.verify_generated_headers:
+ linesep = self.policy.linesep.encode()
+ if not folded.endswith(linesep):
+ raise HeaderWriteError(
+ f'folded header does not end with {linesep!r}: {folded!r}')
+ if NEWLINE_WITHOUT_FWSP_BYTES.search(folded.removesuffix(linesep)):
+ raise HeaderWriteError(
+ f'folded header contains newline: {folded!r}')
+ self._fp.write(folded)
# A blank line always separates headers from body
self.write(self._NL)
diff --git a/Lib/test/test_email/test_generator.py b/Lib/test/test_email/test_generator.py
index c75a842c33578e..3ca79edf6a65d9 100644
--- a/Lib/test/test_email/test_generator.py
+++ b/Lib/test/test_email/test_generator.py
@@ -313,7 +313,7 @@ def test_flatten_unicode_linesep(self):
self.assertEqual(s.getvalue(), self.typ(expected))
def test_verify_generated_headers(self):
- """gh-121650: by default the generator prevents header injection"""
+ # gh-121650: by default the generator prevents header injection
class LiteralHeader(str):
name = 'Header'
def fold(self, **kwargs):
@@ -334,6 +334,8 @@ def fold(self, **kwargs):
with self.assertRaises(email.errors.HeaderWriteError):
message.as_string()
+ with self.assertRaises(email.errors.HeaderWriteError):
+ message.as_bytes()
class TestBytesGenerator(TestGeneratorBase, TestEmailBase):
diff --git a/Lib/test/test_email/test_policy.py b/Lib/test/test_email/test_policy.py
index baa35fd68e49c5..71ec0febb0fd86 100644
--- a/Lib/test/test_email/test_policy.py
+++ b/Lib/test/test_email/test_policy.py
@@ -296,7 +296,7 @@ def test_short_maxlen_error(self):
policy.fold("Subject", subject)
def test_verify_generated_headers(self):
- """Turning protection off allows header injection"""
+ # Turning protection off allows header injection
policy = email.policy.default.clone(verify_generated_headers=False)
for text in (
'Header: Value\r\nBad: Injection\r\n',
@@ -319,6 +319,10 @@ def fold(self, **kwargs):
message.as_string(),
f"{text}\nBody",
)
+ self.assertEqual(
+ message.as_bytes(),
+ f"{text}\nBody".encode(),
+ )
# XXX: Need subclassing tests.
# For adding subclassed objects, make sure the usual rules apply (subclass
diff --git a/Misc/NEWS.d/next/Security/2026-01-21-12-34-05.gh-issue-144125.TAz5uo.rst b/Misc/NEWS.d/next/Security/2026-01-21-12-34-05.gh-issue-144125.TAz5uo.rst
new file mode 100644
index 00000000000000..e6333e724972c5
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2026-01-21-12-34-05.gh-issue-144125.TAz5uo.rst
@@ -0,0 +1,4 @@
+:mod:`~email.generator.BytesGenerator` will now refuse to serialize (write) headers
+that are unsafely folded or delimited; see
+:attr:`~email.policy.Policy.verify_generated_headers`. (Contributed by Bas
+Bloemsaat and Petr Viktorin in :gh:`121650`).

7
python313.changes
View File

@@ -1,3 +1,10 @@
-------------------------------------------------------------------
Tue Jan 27 16:31:12 UTC 2026 - Matej Cepl <mcepl@cepl.eu>
- Add CVE-2024-6923-follow-up-EOL-email-headers.patch which is
a follow-up to the previous fix of CVE-2024-6923 further
encoding EOL possibly hidden in email headers (bsc#1257181).
-------------------------------------------------------------------
Thu Dec 11 21:36:09 UTC 2025 - Matej Cepl <mcepl@cepl.eu>

5
python313.spec
View File

@@ -238,6 +238,11 @@ Patch45: gh139257-Support-docutils-0.22.patch
# PATCH-FIX-UPSTREAM pass-test_write_read_limited_history.patch bsc#[0-9]+ mcepl@suse.com
# Fix readline history truncation when length is reduced
Patch48: pass-test_write_read_limited_history.patch
# PATCH-FIX-UPSTREAM CVE-2024-6923-follow-up-EOL-email-headers.patch bsc#1257181 mcepl@suse.com
# Encode newlines in headers when using ByteGenerator
# patch from gh#python/cpython#144125
Patch49: CVE-2024-6923-follow-up-EOL-email-headers.patch
#### END OF PATCHES
BuildRequires: autoconf-archive
BuildRequires: automake
BuildRequires: fdupes