We take the security of
cryptography seriously. The following are a set of
policies we have adopted to ensure that security issues are addressed in a
In addition to
cryptography’s code, we’re also concerned with the security
of the infrastructure we run (primarily
cryptography.io). If you discover
a security vulnerability in our infrastructure, we ask you to report it using
the same procedure.
What is a security issue?¶
Anytime it’s possible to write code using
cryptography’s public API which
does not provide the guarantees that a reasonable developer would expect it to
based on our documentation.
That’s a bit academic, but basically it means the scope of what we consider a
vulnerability is broad, and we do not require a proof of concept or even a
specific exploit, merely a reasonable threat model under which
could be attacked.
To give a few examples of things we would consider security issues:
If a recipe, such as Fernet, made it easy for a user to bypass confidentiality or integrity with the public API (e.g. if the API let a user reuse nonces).
If, under any circumstances, we used a CSPRNG which wasn’t fork-safe.
cryptographyused an API in an underlying C library and failed to handle error conditions safely.
Examples of things we wouldn’t consider security issues:
Offering ECB mode for symmetric encryption in the Hazmat layer. Though ECB is critically weak, it is documented as being weak in our documentation.
Using a variable time comparison somewhere, if it’s not possible to articulate any particular program in which this would result in problematic information disclosure.
In general, if you’re unsure, we request that you to default to treating things as security issues and handling them sensitively, the worst thing that can happen is that we’ll ask you to file a public issue.
Reporting a security issue¶
We ask that you do not report security issues to our normal GitHub issue tracker.
If you believe you’ve identified a security issue with
report it to
should verify that your MTA uses TLS to ensure the confidentiality of your
Once you’ve submitted an issue via email, you should receive an acknowledgment within 48 hours, and depending on the action to be taken, you may receive further follow-up emails.
At any given time, we will provide security support for the main branch as well as the most recent release.
New releases for OpenSSL updates¶
As of versions 0.5, 1.0.1, and 2.0.0,
cryptography statically links OpenSSL
in binary distributions for Windows, macOS, and Linux respectively, to ease
installation. Due to this,
cryptography will release a new version whenever
OpenSSL has a security or bug fix release to avoid shipping insecure software.
Like all our other releases, this will be announced on the mailing list and we strongly recommend that you upgrade as soon as possible.
When we become aware of a security bug in
cryptography, we will endeavor to
fix it and issue a release as quickly as possible. We will generally issue a new
release for any security issue.
The steps for issuing a security release are described in our Doing a release documentation.