USN-8018-2: Python regression

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. (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.

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