CVE-2020-9702 in Acrobat Reader
Summary
by MITRE
Adobe Acrobat and Reader versions 2020.009.20074 and earlier, 2020.001.30002, 2017.011.30171 and earlier, and 2015.006.30523 and earlier have a stack exhaustion vulnerability. Successful exploitation could lead to application denial-of-service.
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Analysis
by VulDB Data Team • 11/08/2020
Adobe Acrobat and Reader applications contain a stack exhaustion vulnerability that affects multiple product versions including 2020.009.20074 and earlier, 2020.001.30002, 2017.011.30171 and earlier, and 2015.006.30523 and earlier. This vulnerability stems from improper handling of recursive operations within the software's parsing mechanisms, particularly when processing maliciously crafted pdf files. The flaw manifests when the application attempts to recursively process nested structures without adequate stack depth monitoring or termination conditions, leading to exhaustion of the available stack space. This vulnerability aligns with CWE-772, which describes insufficient resource management, and specifically relates to stack-based buffer overflows or exhaustion conditions that occur during recursive function calls. The technical implementation involves the application's failure to validate the depth of recursive operations when parsing pdf objects, particularly in complex nested structures such as arrays, dictionaries, or streams that may contain self-referential elements.
The operational impact of this vulnerability presents a significant denial-of-service risk to users who encounter maliciously crafted pdf documents. When exploited, the vulnerability causes the targeted application to crash or become unresponsive, effectively rendering the software unusable for the affected user. Attackers can leverage this weakness by crafting pdf files containing deeply nested recursive structures that trigger the stack exhaustion condition upon document opening or processing. The vulnerability does not appear to enable arbitrary code execution or privilege escalation, but rather focuses on disrupting service availability. From an attacker perspective, this represents a low-effort, high-impact vector for disrupting productivity, as the exploitation requires only the delivery of a malicious pdf file without any user interaction beyond opening the document. This vulnerability maps to attack techniques described in the MITRE ATT&CK framework under the T1499 category, which covers network denial of service attacks, and specifically relates to T1499.004 for network denial of service via application or service.
Organizations should implement immediate mitigation strategies including applying the latest security patches from Adobe, which address the stack exhaustion issue by implementing proper recursion depth limits and stack management controls. System administrators should also consider implementing pdf content filtering solutions that can detect and block suspicious nested structures before they reach end-user systems. Additional defensive measures include restricting user access to pdf files from untrusted sources, implementing sandboxing mechanisms for pdf processing, and monitoring for unusual application behavior that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper resource management in security-critical applications and highlights the need for comprehensive input validation and recursive operation controls. Organizations should also consider implementing automated vulnerability scanning tools that can identify potentially malicious pdf files based on structural patterns that may indicate stack exhaustion vulnerabilities. Regular security awareness training should emphasize the risks of opening pdf files from unknown sources, as this vulnerability can be effectively exploited through social engineering attacks that deliver malicious documents to unsuspecting users.