CVE-2020-11067 in TYPO3
Summary
by MITRE
In TYPO3 CMS 9.0.0 through 9.5.16 and 10.0.0 through 10.4.1, it has been discovered that backend user settings (in $BE_USER->uc) are vulnerable to insecure deserialization. In combination with vulnerabilities of third party components, this can lead to remote code execution. A valid backend user account is needed to exploit this vulnerability. This has been fixed in 9.5.17 and 10.4.2.
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Analysis
by VulDB Data Team • 10/18/2020
The vulnerability identified as CVE-2020-11067 represents a critical insecure deserialization flaw within TYPO3 CMS versions ranging from 9.0.0 through 9.5.16 and 10.0.0 through 10.4.1. This vulnerability specifically targets the backend user settings storage mechanism where user configuration data is persisted in the $BE_USER->uc variable. The insecure deserialization occurs when the system processes user settings that have been serialized and stored in the database, creating an attack surface that can be exploited by malicious actors who have obtained valid backend user credentials. The flaw stems from the application's failure to properly validate and sanitize serialized data before deserializing it back into executable code objects.
The technical implementation of this vulnerability allows attackers with valid backend user accounts to manipulate serialized data structures within the user configuration settings. When the TYPO3 CMS processes these serialized objects, it performs deserialization without adequate input validation, enabling attackers to craft malicious serialized payloads that can execute arbitrary code on the server. This type of vulnerability falls under CWE-502 which specifically addresses deserialization of untrusted data, and aligns with ATT&CK technique T1059.007 for command and script injection. The exploitation requires a valid backend account, but once achieved, provides attackers with the ability to execute code with the privileges of the web server, potentially leading to complete system compromise.
The operational impact of CVE-2020-11067 extends beyond simple code execution, as it can enable attackers to establish persistent access, escalate privileges, and potentially move laterally within the network infrastructure. The vulnerability's exploitation chain typically involves crafting malicious serialized data that, when processed by the TYPO3 CMS backend, triggers remote code execution. This represents a significant risk for organizations running affected TYPO3 versions, as the attack vector requires only a valid backend user account rather than elevated privileges. The vulnerability's severity is compounded by the fact that it can be combined with other third-party component vulnerabilities to create more sophisticated attack scenarios, making it particularly dangerous in environments where multiple applications share the same infrastructure.
Organizations affected by CVE-2020-11067 should immediately upgrade to TYPO3 versions 9.5.17 and 10.4.2 where the vulnerability has been patched. The fix implements proper input validation and sanitization of serialized data within the backend user settings processing. Additionally, administrators should conduct thorough security assessments of their TYPO3 installations, review user access controls, and implement monitoring for suspicious activities in backend user sessions. Security hardening measures should include restricting backend access through network segmentation, implementing multi-factor authentication, and regularly auditing user accounts for unauthorized access. The vulnerability serves as a reminder of the critical importance of validating serialized data inputs and implementing proper security controls around user configuration management in web applications.