CVE-2020-15098 in TYPO3
Summary
by MITRE
In TYPO3 CMS greater than or equal to 9.0.0 and less than 9.5.20, and greater than or equal to 10.0.0 and less than 10.4.6, it has been discovered that an internal verification mechanism can be used to generate arbitrary checksums. This allows to inject arbitrary data having a valid cryptographic message authentication code (HMAC-SHA1) and can lead to various attack chains including potential privilege escalation, insecure deserialization & remote code execution. The overall severity of this vulnerability is high based on mentioned attack chains and the requirement of having a valid backend user session (authenticated). This has been patched in versions 9.5.20 and 10.4.6.
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Analysis
by VulDB Data Team • 11/06/2020
This vulnerability exists within TYPO3 CMS versions between 9.0.0 and 9.5.19, as well as between 10.0.0 and 10.4.5, where a flaw in the internal verification mechanism permits attackers to generate arbitrary checksums. The technical implementation involves a cryptographic weakness in the HMAC-SHA1 message authentication code generation process, which allows an authenticated attacker with a valid backend user session to manipulate the verification logic. This represents a critical security flaw classified under CWE-347: Improper Verification of Cryptographic Signature, as it undermines the fundamental integrity checks that should protect against tampered data. The vulnerability stems from the predictable nature of the HMAC generation algorithm, which can be exploited to forge valid cryptographic signatures for malicious payloads.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to bypass security controls that rely on HMAC validation for data integrity. An attacker can inject arbitrary data with valid HMAC-SHA1 signatures, creating a pathway for privilege escalation attacks where they can manipulate backend processes and access restricted functionality. The vulnerability also opens possibilities for insecure deserialization attacks, where malicious data structures can be processed without proper validation, potentially leading to remote code execution. This aligns with ATT&CK technique T1059.007 for command and script injection, and T1068 for exploit for privilege escalation. The requirement for an authenticated backend session reduces the attack surface but does not eliminate the severity, as compromised backend credentials represent a significant threat vector in web application security.
The exploitation chain typically begins with an attacker obtaining valid backend credentials through phishing, credential reuse, or other initial compromise techniques. Once authenticated, the attacker can leverage this vulnerability to manipulate internal verification mechanisms, potentially escalating privileges to administrative levels or executing arbitrary code on the server. The patch implemented in versions 9.5.20 and 10.4.6 addresses the core cryptographic implementation by strengthening the HMAC generation process and ensuring proper randomization of checksum values. Security practitioners should prioritize immediate patching of affected systems, as the vulnerability can be exploited without additional prerequisites beyond a valid backend session. Organizations should also implement additional monitoring for suspicious backend activities and consider network segmentation to limit the potential impact of credential compromise, while adhering to security standards such as those outlined in NIST SP 800-53 for secure configuration management and cryptographic key management practices.