CVE Vulnerabilities

CVE-2021-42550

Deserialization of Untrusted Data

Published: Dec 16, 2021 | Modified: Dec 12, 2022
CVSS 3.x
6.6
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
8.5 HIGH
AV:N/AC:M/Au:S/C:C/I:C/A:C
RedHat/V2
RedHat/V3
6.6 MODERATE
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Ubuntu
MEDIUM

In logback version 1.2.7 and prior versions, an attacker with the required privileges to edit configurations files could craft a malicious configuration allowing to execute arbitrary code loaded from LDAP servers.

Weakness

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

Affected Software

Name Vendor Start Version End Version
Logback Qos * 1.2.7 (including)
Logback Qos 1.3.0-alpha0 (including) 1.3.0-alpha0 (including)
Logback Qos 1.3.0-alpha1 (including) 1.3.0-alpha1 (including)
Logback Qos 1.3.0-alpha10 (including) 1.3.0-alpha10 (including)
Logback Qos 1.3.0-alpha2 (including) 1.3.0-alpha2 (including)
Logback Qos 1.3.0-alpha3 (including) 1.3.0-alpha3 (including)
Logback Qos 1.3.0-alpha4 (including) 1.3.0-alpha4 (including)
Logback Qos 1.3.0-alpha5 (including) 1.3.0-alpha5 (including)
Logback Qos 1.3.0-alpha6 (including) 1.3.0-alpha6 (including)
Logback Qos 1.3.0-alpha7 (including) 1.3.0-alpha7 (including)
Logback Qos 1.3.0-alpha8 (including) 1.3.0-alpha8 (including)
Logback Qos 1.3.0-alpha9 (including) 1.3.0-alpha9 (including)
Logback Ubuntu bionic *
Logback Ubuntu hirsute *
Logback Ubuntu impish *
Logback Ubuntu kinetic *
Logback Ubuntu lunar *
Logback Ubuntu mantic *
Logback Ubuntu trusty *
Logback Ubuntu upstream *
Logback Ubuntu xenial *
Red Hat Fuse 7.11 RedHat logback-classic *
Red Hat Satellite 6.11 for RHEL 7 RedHat candlepin-0:4.1.13-1.el7sat *
Red Hat Satellite 6.11 for RHEL 8 RedHat candlepin-0:4.1.13-1.el8sat *
RHDM 7.12.1 RedHat logback-classic *
RHPAM 7.12.1 RedHat logback-classic *

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