CVE-2018-10903

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.

• CWE-20
• CWE-20

• https://access.redhat.com/errata/RHSA-2018:3600
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903Issue Tracking, Patch, Third Party Advisory
• https://github.com/pyca/cryptography/pull/4342/commits/688e0f673bfbf43fa898994326c6877f00ab19efPatch, Third Party Advisory
• https://usn.ubuntu.com/3720-1/Third Party Advisory
• https://access.redhat.com/errata/RHSA-2018:3600
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903Issue Tracking, Patch, Third Party Advisory
• https://github.com/pyca/cryptography/pull/4342/commits/688e0f673bfbf43fa898994326c6877f00ab19efPatch, Third Party Advisory
• https://usn.ubuntu.com/3720-1/Third Party Advisory

Published

Jul 30, 2018

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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