CVE-2020-13586 in Office
Summary
by MITRE • 02/04/2021
A memory corruption vulnerability exists in the Excel Document SST Record 0x00fc functionality of SoftMaker Software GmbH SoftMaker Office PlanMaker 2021 (Revision 1014). A specially crafted malformed file can lead to a heap buffer overflow. An attacker can provide a malicious file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 02/23/2021
The vulnerability identified as CVE-2020-13586 represents a critical memory corruption issue within SoftMaker Office PlanMaker 2021 software, specifically affecting the Excel Document SST Record 0x00fc functionality. This flaw resides in the handling of structured storage table records within spreadsheet files, where the application fails to properly validate input data before processing. The vulnerability stems from inadequate bounds checking mechanisms that allow maliciously crafted data to overflow allocated memory buffers during parsing operations. The affected component processes string storage tables that contain formatted text data, making it particularly dangerous as it can be triggered through standard spreadsheet file operations.
The technical implementation of this heap buffer overflow occurs when PlanMaker processes malformed Excel files containing specially crafted SST records with the hexadecimal identifier 0x00fc. During the parsing sequence, the application allocates memory for string storage but does not adequately verify the length of incoming data against allocated buffer boundaries. This allows an attacker to inject excessive data that overflows the designated heap memory region, potentially corrupting adjacent memory structures. The vulnerability manifests as a classic buffer overflow condition where the application writes beyond the allocated memory space, creating opportunities for arbitrary code execution or application crash scenarios. According to CWE classification, this corresponds to CWE-121, heap-based buffer overflow, which directly relates to improper bounds checking in memory management operations.
The operational impact of this vulnerability extends beyond simple application instability, presenting significant security risks to users of SoftMaker Office PlanMaker 2021. An attacker capable of delivering a malicious file to a victim's system can potentially execute remote code with the privileges of the affected user, leading to complete system compromise. The vulnerability is particularly concerning because it can be triggered through normal file opening operations without requiring special user interaction beyond opening the malicious document. This makes it susceptible to phishing attacks, malicious email attachments, or compromised file sharing platforms where users might inadvertently open infected spreadsheet files. The exploitability of this vulnerability aligns with ATT&CK technique T1204.002, legitimate user execution, as it requires only normal application usage patterns to achieve successful exploitation.
Mitigation strategies for CVE-2020-13586 should prioritize immediate software updates from SoftMaker to address the underlying memory handling flaws. Organizations should implement strict file validation policies, particularly for spreadsheet files from untrusted sources, and consider deploying sandboxing mechanisms for document processing. Network-based protections can include filtering Excel file extensions at perimeter defenses and implementing advanced threat detection systems that monitor for anomalous memory access patterns. Users should be educated about the risks of opening unknown or untrusted spreadsheet files, and security teams should monitor for indicators of compromise related to this vulnerability. The fix typically involves implementing proper bounds checking and input validation mechanisms in the SST record processing logic, ensuring that all data lengths are verified against allocated buffer sizes before memory operations occur. Additionally, memory protection features such as data execution prevention and address space layout randomization should be enabled to reduce exploit reliability even if the underlying vulnerability cannot be immediately patched.