CVE Vulnerabilities

CVE-2021-32742

Deserialization of Untrusted Data

Published: Jul 09, 2021 | Modified: Jul 22, 2021
CVSS 3.x
9.1
CRITICAL
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CVSS 2.x
6.4 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:P
RedHat/V2
RedHat/V3
Ubuntu

Vapor is a web framework for Swift. In versions 4.47.1 and prior, bug in the Data.init(base32Encoded:) function opens up the potential for exposing server memory and/or crashing the server (Denial of Service) for applications where untrusted data can end up in said function. Vapor does not currently use this function itself so this only impact applications that use the impacted function directly or through other dependencies. The vulnerability is patched in version 4.47.2. As a workaround, one may use an alternative to Vapors built-in Data.init(base32Encoded:).

Weakness

The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.

Affected Software

Name Vendor Start Version End Version
Vapor Vapor_project * 4.47.2 (excluding)

Extended Description

It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.

Potential Mitigations

  • Make fields transient to protect them from deserialization.
  • An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.

References