CVE-2011-1512 in Lotus Notes
Summary
by MITRE
Heap-based buffer overflow in xlssr.dll in Autonomy KeyView, as used in IBM Lotus Notes before 8.5.2 FP3, allows remote attackers to execute arbitrary code via a malformed BIFF record in a .xls Excel spreadsheet attachment, aka SPR PRAD8E3HKR.
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Analysis
by VulDB Data Team • 11/08/2021
The vulnerability identified as CVE-2011-1512 represents a critical heap-based buffer overflow flaw within the xlssr.dll component of Autonomy KeyView software, which was subsequently integrated into IBM Lotus Notes products. This vulnerability specifically affects versions of IBM Lotus Notes prior to 8.5.2 Fix Pack 3, creating a significant security risk that could be exploited by remote attackers to gain unauthorized system control. The flaw manifests when the affected software processes malformed BIFF (Binary Interchange File Format) records contained within .xls Excel spreadsheet attachments, making it particularly dangerous in email environments where such attachments are commonly exchanged.
The technical nature of this vulnerability stems from improper input validation within the xlssr.dll library responsible for parsing Microsoft Excel file formats. When processing a specially crafted BIFF record structure, the software fails to properly bounds-check memory allocations, leading to a situation where data written to heap memory exceeds the allocated buffer size. This heap corruption creates opportunities for attackers to overwrite adjacent memory locations, potentially allowing them to inject and execute arbitrary code with the privileges of the targeted application. The vulnerability operates at the application layer and requires no special privileges to exploit, making it particularly dangerous in enterprise environments where Lotus Notes is widely deployed.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to potentially compromise entire email servers and client systems that process Lotus Notes attachments. IBM Lotus Notes serves as a critical communication platform for many enterprises, making this vulnerability particularly attractive to threat actors seeking persistent access to organizational networks. The remote exploitation capability means that attackers can trigger the vulnerability simply by sending a malicious Excel attachment, without requiring physical access to the target system. This characteristic aligns with ATT&CK technique T1193, which describes the use of malicious attachments to gain initial access to systems. The vulnerability also relates to CWE-121, heap-based buffer overflow, which is a common class of memory corruption vulnerabilities that can lead to arbitrary code execution.
Organizations affected by this vulnerability should prioritize immediate remediation through the application of IBM Lotus Notes 8.5.2 Fix Pack 3, which contains the necessary patches to address the heap overflow condition in xlssr.dll. Security administrators should also implement network-based controls such as email filtering rules that block or scan .xls attachments from untrusted sources, as well as consider disabling automatic preview of Excel attachments within the Lotus Notes client. Additionally, monitoring for unusual network activity or system behavior that might indicate exploitation attempts should be implemented, particularly focusing on processes related to Excel file parsing and memory allocation patterns. The vulnerability demonstrates the importance of maintaining up-to-date software libraries and the risks associated with legacy components that may contain unpatched security flaws, reinforcing the need for comprehensive vulnerability management programs that address both known and emerging threats in enterprise email systems.