CVE-2018-10903: PyCA Cryptography vulnerable to GCM tag forgery
(updated )
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.
References
- access.redhat.com/errata/RHSA-2018:3600
- bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903
- github.com/advisories/GHSA-fcf9-3qw3-gxmj
- github.com/pyca/cryptography
- github.com/pyca/cryptography/commit/d4378e42937b56f473ddade2667f919ce32208cb
- github.com/pyca/cryptography/pull/4342
- github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2018-52.yaml
- nvd.nist.gov/vuln/detail/CVE-2018-10903
- usn.ubuntu.com/3720-1
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