Python Cryptographic Authority python-cryptography finalize_with_tag API Information Disclosure Vulnerability [CVE-2018-10903]

CVE Number – CVE-2018-10903

A vulnerability in the finalize_with_tag API of Python Cryptographic Authority python-cryptography could allow an unauthenticated, remote attacker to access sensitive information on a targeted system.

The vulnerability is due to insufficient enforcement of a minimum tag length prior to passing user-supplied input to the finalize_with_tag API of the affected software. An attacker could exploit this vulnerability by sending a request that submits a malicious short tag length to the targeted system. A successful exploit could cause key leakage, which could allow the attacker to access sensitive information. 

Python Cryptographic Authority has confirmed the vulnerability and released software updates.


  • To exploit this vulnerability, an attacker must send a request that submits malicious input to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.


  • Administrators are advised to apply the appropriate updates.

    Administrators are advised to allow only trusted users to have network access.

    Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.

    Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

    Administrators can help protect affected systems from external attacks by using a solid firewall strategy.

    Administrators are advised to monitor affected systems.

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Fixed Software

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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