CVE-2018-10903: PyCA Cryptography vulnerable to GCM tag forgery

CVE-2018-10903 · Severity: low · CVSS 3 · Published 2018-07-30

A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.

Technologies: cryptography (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2018-10903 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2018-10903 being exploited in the wild.
How severe is CVE-2018-10903?
Low severity, with a CVSS score of 3, published 30 July 2018.
Which products and versions are affected?
cryptography (PyPI) ECOSYSTEM:introduced=1.9,fixed=2.3, ECOSYSTEM:introduced=1.9.0,fixed=2.3.
Is there a fix for CVE-2018-10903?
Yes. cryptography (PyPI): upgrade to 2.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2018-10903?
Check whether you run cryptography (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • cryptography (PyPI): upgrade to 2.3 or later
    pip install "cryptography>=2.3"

Affected products

  • cryptography (PyPI) ECOSYSTEM:introduced=1.9,fixed=2.3, ECOSYSTEM:introduced=1.9.0,fixed=2.3

Identifiers

  • CVE-2018-10903
  • GHSA-fcf9-3qw3-gxmj
  • PYSEC-2018-52

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