chore(deps): bump cryptography from 46.0.7 to 50.0.0 in /backend

[dependabot]

Bumps cryptography from 46.0.7 to 50.0.0.

Changelog

Sourced from cryptography's changelog.

50.0.0 - 2026-07-31

* **SECURITY ISSUE**:
  :func:`~cryptography.hazmat.primitives.serialization.pkcs7.pkcs7_decrypt_der`
  and its PEM and S/MIME variants no longer expose distinguishable errors or
  timing when unwrapping a ``RecipientInfo``'s ``encryptedKey``, which could
  act as a Bleichenbacher oracle for callers that decrypt untrusted messages.
  A random key is now substituted on failure, as described in :rfc:`3218`.
  Credit to **@X1AOxiang** for reporting the issue. **CVE-2026-69247**
* Deprecated Diffie-Hellman key exchange over finite fields (FFDH).
  Everything FFDH is deprecated, including the types in
  ``cryptography.hazmat.primitives.asymmetric.dh`` and loading FFDH keys or
  parameters with the key loading APIs. Users should migrate to a more
  modern key exchange algorithm.
* Added ``xof()`` class methods to
  :class:`~cryptography.hazmat.primitives.hashes.SHAKE128` and
  :class:`~cryptography.hazmat.primitives.hashes.SHAKE256` for constructing
  algorithm instances configured for use with
  :class:`~cryptography.hazmat.primitives.hashes.XOFHash`.
* The :mod:`X.509 verification <cryptography.x509.verification>` APIs are now
  considered stable and are subject to our API stability policy.
* Added the :doc:`/cobblestone` recipe, an implementation of the
  Cobblestone-128 and Cobblestone-256 instantiations of the `C2SP
  chunked-encryption specification
  <https://c2sp.org/chunked-encryption>`_ for streaming authenticated
  encryption of large messages.
* Parsing a Signed Certificate Timestamp list now rejects encodings that
  carry trailing bytes after the list or after an individual SCT, instead of
  silently ignoring them.
* Added support for using :class:`~cryptography.x509.Name` as a field type in
  the :doc:`/hazmat/asn1/index` module.
* Loading a public key or an EC private key now rejects DER where the
  ``subjectPublicKey`` (or EC ``publicKey``) ``BIT STRING`` declares a non-zero
  number of unused bits, instead of silently ignoring it.
* Parsing a CRL entry's ``InvalidityDate`` extension now rejects a
  ``GeneralizedTime`` that carries fractional seconds or another non-DER form,
  matching the strict encoding already required for every other X.509 time
  field.
* :func:`~cryptography.x509.ocsp.load_der_ocsp_request` and
  :func:`~cryptography.x509.ocsp.load_der_ocsp_response` now reject a request
  or response whose ``version`` field is not ``v1``, the only version defined
  by RFC 6960, matching the version validation already performed when loading
  certificates, CSRs and CRLs.
* :class:`~cryptography.hazmat.primitives.hashes.XOFHash` is now supported
  when building against AWS-LC.
* HMAC (and therefore PBKDF2-HMAC) with SHA-3 hashes is now supported when
  building against AWS-LC.
* Diffie-Hellman (:doc:`/hazmat/primitives/asymmetric/dh`) is now supported
  when building against AWS-LC.
</tr></table> 

... (truncated)

Commits

• dcb7050 Prepare for 50.0.0 release (#15372)
• 53fccd9 Don't leak how PKCS#7 encryptedKey decryption failed (#15369)
• d472f97 Add from __future__ import annotations to all src/ Python files (#15371)
• 908773d Bump downstream dependencies in CI (#15368)
• 2cc07cc Bump BoringSSL, OpenSSL, AWS-LC in CI (#15367)
• c94ede9 chore(deps): bump ruff from 0.16.0 to 0.16.1 (#15366)
• 67a8308 chore(deps): bump virtualenv from 21.7.0 to 21.7.1 (#15365)
• 95018ff Release the GIL in one-shot AEAD encrypt/decrypt (#15361)
• 6954733 Release the GIL during DH and DSA parameter generation (#15364)
• 6893b94 Import _serialization instead of serialization in x509/extensions (#15363)
• Additional commits viewable in compare view

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Project	Deployment	Actions	Updated (UTC)
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[llamapreview]

LlamaPReview — No blocking issues found

Approve: bumping cryptography to 50.0.0 is safe for this repo because no first-party code uses it, only transitive deps aiortc and pyopenssl do.

1 non-blocking finding retained — highest: No first-party cryptography usage makes major-version bump safe.

Change flow

The install-path fork determines whether this pin swap has any runtime effect — the core install decision this PR touches.

sequenceDiagram
    participant Dev as Developer
    participant Repo as Repo (pyproject.toml, uv.lock)
    participant Export as uv export
    participant CI as CI/Prod install
    Dev->>Repo: Declare deps & lock
    Repo->>Export: uv export generates requirements.txt
    note over Export: PR change — cryptography pinned 50.0.0
    alt Install from requirements.txt
        Export->>CI: Install cryptography==50.0.0
    else Install via uv sync
        Repo->>CI: Use uv.lock resolution<br/>may still be old pin
    end

Loading

Review details and evidence

Priority	File	Finding	Evidence
P2	backend/requirements.txt	No first-party cryptography usage makes major-version bump safe.	confirmed

Material unknowns

• Whether backend/uv.lock resolves cryptography at 50.0.0 and whether production installs from requirements.txt or via uv sync. If uv.lock pins below 50.0.0 and installs use uv sync, this PR has no effect; a future uv export regeneration would overwrite the pin. If production installs from requirements.txt, the bump applies directly.
  • Check: Check the cryptography entry in backend/uv.lock and the install command used in CI/production; if the lockfile is below 50.0.0, update pyproject.toml/uv.lock and regenerate the export.
• cryptography 50.0.0's minimum Python version relative to the project's >=3.11 floor. If 50.0.0 raised its Python floor above 3.11, installs would fail; Deep assessed this as minimal risk because the floor is well above historical values.
  • Check: Run a one-time install evaluation (pip install -r backend/requirements.txt or uv export) to confirm compatibility.

LlamaPReview checks

• Inspected matching PR-head repository snippets in backend/requirements.txt.
• Read bounded PR-head context from backend/requirements.txt.
• Read bounded PR-head context from backend/pyproject.toml.

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Automated review by LlamaPReview · Free for public open-source projects.

[llamapreview]

P2 | Confidence: Medium

The change is a single pin swap in a generated requirements file. Deep found no first-party code using cryptography, cryptography.hazmat, or pkcs7 — the only references are the transitive via-lines aiortc and pyopenssl. Therefore the announced breaking changes (PKCS#7 fix, FFDH deprecation, stricter parsing) have no observed reachable path. CI is green on deploy checks; CodeQL is neutral with no findings. The residual risks are unobserved transitive compatibility and install-path durability.

Owner action: Optional: run a backend smoke test of the WebRTC/DTLS path to confirm aiortc works with the new pin.

Evidence: matching repository snippets in backend/requirements.txt; bounded PR-head context from backend/requirements.txt; bounded PR-head context from backend/pyproject.toml.