USN-8018-2: Python regression

Publication date

9 March 2026

Overview

USN-8018-1 introduced a regression in Python


Packages

  • python3.10 - An interactive high-level object-oriented language
  • python3.11 - An interactive high-level object-oriented language
  • python3.12 - An interactive high-level object-oriented language
  • python3.13 - An interactive high-level object-oriented language
  • python3.14 - An interactive high-level object-oriented language
  • python3.4 - An interactive high-level object-oriented language
  • python3.5 - An interactive high-level object-oriented language
  • python3.6 - An interactive high-level object-oriented language
  • python3.7 - An interactive high-level object-oriented language
  • python3.8 - An interactive high-level object-oriented language
  • python3.9 - An interactive high-level object-oriented language

Details

USN-8018-1 fixed vulnerabilities in python3. That update introduced
regressions. The patches for CVE-2025-15366 and CVE-2025-15367 caused
behavior regressions in IMAP and POP3 handling, which upstream chose to
avoid by not backporting them. Additionally, the patch for CVE-2026-0865
incorrectly rejected horizontal tabs in wsgiref headers. This update fixes
these problems.

We apologize for the inconvenience.

Original advisory details:

Denis Ledoux discovered that Python incorrectly parsed email message
headers. An attacker could possibly use this issue to inject arbitrary
headers into email messages. This issue only affected python3.6,
python3.7, python3.8, python3.9, python3.10, python3.11, python3.12,
python3.13, and python3.14 packages. (

USN-8018-1 fixed vulnerabilities in python3. That update introduced
regressions. The patches for CVE-2025-15366 and CVE-2025-15367 caused
behavior regressions in IMAP and POP3 handling, which upstream chose to
avoid by not backporting them. Additionally, the patch for CVE-2026-0865
incorrectly rejected horizontal tabs in wsgiref headers. This update fixes
these problems.

We apologize for the inconvenience.

Original advisory details:

Denis Ledoux discovered that Python incorrectly parsed email message
headers. An attacker could possibly use this issue to inject arbitrary
headers into email messages. This issue only affected python3.6,
python3.7, python3.8, python3.9, python3.10, python3.11, python3.12,
python3.13, and python3.14 packages. (CVE-2025-11468)

Jacob Walls, Shai Berger, and Natalia Bidart discovered that Python
inefficiently parsed XML input with quadratic complexity. An attacker
could possibly use this issue to cause a denial of service.
(CVE-2025-12084)

It was discovered that Python incorrectly parsed malicious plist files. An
attacker could possibly use this issue to cause Python to use excessive
resources, leading to a denial of service. This issue only affected
python3.5, python3.6, python3.7, python3.8, python3.9, python3.10,
python3.11, python3.12, python3.13, and python3.14 packages.
(CVE-2025-13837)

Omar Hasan discovered that Python incorrectly parsed URL mediatypes. An
attacker could possibly use this issue to inject arbitrary HTTP headers.
(CVE-2025-15282)

Omar Hasan discovered that Python incorrectly parsed malicious IMAP
inputs. An attacker could possibly use this issue to inject arbitrary
IMAP commands. (CVE-2025-15366)

Omar Hasan discovered that Python incorrectly parsed malicious POP3
inputs. An attacker could possibly use this issue to inject arbitrary
POP3 commands. (CVE-2025-15367)

Omar Hasan discovered that Python incorrectly parsed malicious HTTP cookie
headers. An attacker could possibly use this issue to inject arbitrary
HTTP headers. (CVE-2026-0672)

Omar Hasan discovered that Python incorrectly parsed malicious HTTP header
names and values. An attacker could possibly use this issue to inject
arbitrary HTTP headers. (CVE-2026-0865)


Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:

Ubuntu Release Package Version
25.10 questing libpython3.13 –  3.13.7-1ubuntu0.4
libpython3.14 –  3.14.0-1ubuntu0.3
python3.13 –  3.13.7-1ubuntu0.4
python3.14 –  3.14.0-1ubuntu0.3
24.04 LTS noble libpython3.12t64 –  3.12.3-1ubuntu0.12
python3.12 –  3.12.3-1ubuntu0.12
22.04 LTS jammy libpython3.10 –  3.10.12-1~22.04.15
libpython3.11 –  3.11.0~rc1-1~22.04.1~esm9  
python3.10 –  3.10.12-1~22.04.15
python3.11 –  3.11.0~rc1-1~22.04.1~esm9  
20.04 LTS focal libpython3.8 –  3.8.10-0ubuntu1~20.04.18+esm6  
libpython3.9 –  3.9.5-3ubuntu0~20.04.1+esm10  
python3.8 –  3.8.10-0ubuntu1~20.04.18+esm6  
python3.9 –  3.9.5-3ubuntu0~20.04.1+esm10  
18.04 LTS bionic libpython3.6 –  3.6.9-1~18.04ubuntu1.13+esm9  
libpython3.7 –  3.7.5-2ubuntu1~18.04.2+esm10  
libpython3.8 –  3.8.0-3ubuntu1~18.04.2+esm10  
python3.6 –  3.6.9-1~18.04ubuntu1.13+esm9  
python3.7 –  3.7.5-2ubuntu1~18.04.2+esm10  
python3.8 –  3.8.0-3ubuntu1~18.04.2+esm10  
16.04 LTS xenial libpython3.5 –  3.5.2-2ubuntu0~16.04.13+esm22  
python3.5 –  3.5.2-2ubuntu0~16.04.13+esm22  
14.04 LTS trusty libpython3.4 –  3.4.3-1ubuntu1~14.04.7+esm20  
libpython3.5 –  3.5.2-2ubuntu0~16.04.4~14.04.1+esm10  
python3.4 –  3.4.3-1ubuntu1~14.04.7+esm20  
python3.5 –  3.5.2-2ubuntu0~16.04.4~14.04.1+esm10  

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