CVE-2026-0895 in Mailqueue Extension
Summary
by MITRE • 01/20/2026
The extension extends TYPO3’ FileSpool component, which was vulnerable to Insecure Deserialization prior to TYPO3-CORE-SA-2026-004 https://typo3.org/security/advisory/typo3-core-sa-2026-004 . Since the related fix is overwritten by the extension, using the extension with a patched TYPO3 core version still allows for Insecure Deserialization, because the affected vulnerable code was extracted from TYPO3 core to the extension. More information about this vulnerability can be found in the related TYPO3 Core Security Advisory TYPO3-CORE-SA-2026-004 https://typo3.org/security/advisory/typo3-core-sa-2026-004 .
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Analysis
by VulDB Data Team • 01/20/2026
The vulnerability described in CVE-2026-0895 represents a critical security flaw within the TYPO3 content management system ecosystem, specifically targeting the FileSpool component that was previously identified in TYPO3-CORE-SA-2026-004. This issue demonstrates how third-party extensions can inadvertently reintroduce previously patched security vulnerabilities by extracting and modifying vulnerable code components from the core system. The extension in question effectively overrides the security fix implemented in the TYPO3 core, creating a false sense of security for administrators who believe their systems are protected due to a patched core version. This scenario exemplifies the dangerous practice of code extraction without proper security review, where the security remediation efforts of the core development team become ineffective when extension developers reintroduce the vulnerable functionality.
The technical flaw stems from insecure deserialization practices within the FileSpool component, which allows attackers to manipulate serialized data structures during the file processing operations. This vulnerability type maps directly to CWE-502, which categorizes insecure deserialization as a critical weakness that can lead to remote code execution, privilege escalation, and complete system compromise. The attack vector typically involves crafting malicious serialized objects that, when processed by the vulnerable component, trigger unintended code execution within the application context. The extension's design effectively bypasses the core security mechanisms by maintaining the original vulnerable deserialization logic while potentially adding additional attack surface through its own implementation.
The operational impact of this vulnerability extends beyond simple exploitation capabilities to encompass broader security posture degradation within TYPO3 installations. Organizations using affected extensions may experience unauthorized access to system resources, data breaches, and potential complete system compromise even when their core TYPO3 installation appears to be patched. This creates a particularly dangerous scenario where security updates appear to be effective but are undermined by extension-level modifications. The vulnerability affects the availability, integrity, and confidentiality of system resources, as attackers can leverage the insecure deserialization to execute arbitrary commands, modify system files, or extract sensitive information from the database. The persistence of this vulnerability through patched core versions highlights the importance of comprehensive security auditing of all installed extensions and the need for strict security controls around third-party code integration.
Mitigation strategies for this vulnerability require immediate action to either remove the affected extension from the system or implement comprehensive security controls around its usage. System administrators should conduct thorough inventory audits of all installed extensions to identify those that may contain vulnerable code extracted from the core TYPO3 components. The recommended approach involves disabling or removing the vulnerable extension until a secure version is available, while also implementing network-level controls such as firewalls and intrusion detection systems to monitor for potential exploitation attempts. Additionally, organizations should establish strict extension vetting procedures that include security code reviews and vulnerability assessments before installation, as well as regular monitoring for security advisories that may affect their extension ecosystem. This vulnerability also underscores the importance of following ATT&CK framework principles for defensive measures, particularly focusing on privilege separation, input validation, and application whitelisting to prevent exploitation of insecure deserialization vulnerabilities.