The biggest security difference is support: Python 2.7 stopped receiving fixes on 1 January 2020, so every newly found flaw stays open. Python 3 also removed some traps, such as an input function that evaluated what a user typed, and made text and bytes separate types.
Is Python 2 still supported?
No. PEP 373, the Python 2.7 release schedule, says bugfix support officially stopped on 1 January 2020. The last release, 2.7.18, was frozen on that date and shipped on 20 April 2020. Python.org's sunset FAQ is the general overview.
Unsupported means that when a vulnerability is found in the interpreter or the standard library, no upstream patch follows. Third-party packages drift the same way as maintainers drop Python 2. Some Linux vendors have offered their own backports for a time, so check your vendor's terms, but that is a stopgap, not a plan.
What did Python 3 change that matters for security?
The official "What's New in Python 3.0" page lists several changes. Four are relevant.
Input. In Python 2, input() evaluated the typed text as a Python expression, while raw_input() just returned a string. PEP 3111 renamed raw_input() to input(), so the safe behavior became the default. The Python 3.0 page notes that to get the old behavior you must write eval(input()), which makes the dangerous choice visible.
Text and bytes. Python 3 separates text, the str type holding Unicode, from binary data, the bytes type. Python 2 mixed 8-bit strings and Unicode and converted silently. Mixed handling is a classic source of encoding bugs that sometimes turn into validation bypasses, for example when a filter checks one representation and a later step uses another.
Print and iterators. print became a function, and dictionary methods return views instead of lists. These are not security fixes, but they show why an automated conversion is only the first step.
Division and integers. Integer handling was cleaned up, including removing the separate long type. Behavior that changes quietly during migration is a risk in itself, so tests matter.
Does Python 3 make code secure?
No. Injection, unsafe deserialization, weak randomness and path traversal exist in both. Python 3 removes some foot guns and keeps getting fixes, which is the more important point.
How risky is staying on Python 2?
A constructed example: a manufacturer runs an internal reporting tool written in Python 2 that parses uploaded spreadsheets. Nobody wants to touch it. Over several years, vulnerabilities are published in the XML and image libraries it depends on. The newer versions that fix them require Python 3, so the team is stuck on old releases with known flaws, and the tool sits on a network segment with access to production data.
The risk is cumulative: interpreter, libraries and tooling all stop moving together.
How should you migrate?
The 3.0 documentation points to the 2to3 conversion tool for source changes. Use it for a first pass, then run your test suite and add tests around parsing, encoding and anything that handles input from outside. Migrate dependencies at the same time and pin versions. Where migration cannot happen soon, isolate the system: restrict network access, remove internet exposure and add monitoring.
Safeguard's dependency scanning can list the packages in a project and flag known vulnerabilities, which helps you see how many are blocked on a Python 2 pin.
How to check or apply this
- Find every Python 2 script, service and container image. Search for
python2in build files and shebang lines. - Rank them by exposure and data access.
- Add tests before changing code, especially for input handling and encodings.
- Convert, then review every place that used
input(),evalor mixed string types. - Upgrade dependencies and pin the new set.
- For anything that must stay, isolate it and set a removal date.
Quick check
Does Python 2 still get security patches?
Not from the Python project. Support ended on 1 January 2020. Any patches now come from third parties such as an operating system vendor, under their terms.
Sources
Last reviewed: 18 October 2026.
