CVE-2016-7867 in Flash Player
Summary
by MITRE
Adobe Flash Player versions 23.0.0.207 and earlier, 11.2.202.644 and earlier have an exploitable buffer overflow / underflow vulnerability in the RegExp class related to bookmarking in searches. Successful exploitation could lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 10/08/2022
Adobe Flash Player contained a critical buffer overflow vulnerability in its RegExp class implementation that affected versions up to 23.0.0.207 and 11.2.202.644. This vulnerability arose from improper handling of bookmarking operations within search functionality, specifically when processing regular expression patterns that contained malformed or excessively long bookmark references. The flaw manifested as an integer overflow or underflow condition that could be exploited to corrupt memory structures and ultimately achieve arbitrary code execution. The vulnerability falls under CWE-121, which addresses stack-based buffer overflow conditions, and more specifically relates to improper bounds checking in string manipulation operations. Attackers could craft malicious Flash content that, when loaded in affected browsers, would trigger the vulnerable code path during regular expression processing. The exploitation typically involved creating overly complex regular expressions with nested or recursive bookmark references that would cause the Flash Player's internal buffer management to fail. This vulnerability was particularly dangerous because it could be delivered through web browsers without requiring user interaction beyond visiting a malicious website, making it a prime target for drive-by download attacks. The attack surface was extensive given Flash Player's widespread adoption across multiple platforms and browsers. The exploit chain would typically begin with a malicious SWF file hosted on a compromised website, which would then execute the buffer overflow during normal user browsing activities. Organizations were advised to immediately update to patched versions of Flash Player, as Adobe released security updates addressing this specific vulnerability. The incident highlighted the importance of proper input validation and memory safety practices in multimedia frameworks, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage, where attackers could leverage the executed code to establish persistence or escalate privileges. This vulnerability demonstrated how seemingly benign features like search bookmarking could become attack vectors when not properly secured against malformed inputs, emphasizing the need for robust defensive programming practices in complex software systems.
The technical exploitation of this vulnerability required a deep understanding of Flash Player's internal memory management and regular expression engine implementation. The buffer overflow occurred when the player attempted to store bookmark information for complex regular expressions, particularly those with recursive patterns or excessive nesting levels. The vulnerability was classified as a heap-based buffer overflow in many instances, though the exact memory corruption mechanism depended on the specific pattern used in the malicious payload. Attackers could leverage this flaw to overwrite critical memory structures, including return addresses on the stack or function pointers, effectively allowing them to redirect execution flow to malicious code. The exploitation process typically involved crafting a SWF file containing a specially designed regular expression that would trigger the overflow condition when processed by the Flash Player. The vulnerability was particularly challenging to detect and prevent because it occurred during normal application behavior rather than during explicit user input handling. Security researchers noted that the vulnerability could be mitigated through various approaches including browser sandboxing, Flash Player security settings, and network-level filtering. The broader implications of this vulnerability extended beyond immediate exploitation, as it demonstrated how complex multimedia applications could contain security flaws that were difficult to predict and prevent. Organizations implementing security controls needed to consider both client-side and server-side protections, including web application firewalls and content filtering systems. The incident contributed to the broader industry understanding of how legacy multimedia technologies could pose significant security risks when not properly maintained and updated. This vulnerability served as a catalyst for increased focus on Flash Player security and ultimately contributed to the gradual phase-out of Flash technology in favor of more secure web standards. The attack patterns identified for this vulnerability aligned with ATT&CK technique T1203 for exploitation for privilege escalation, where attackers could use the initial code execution to gain higher privileges within the affected system. The vulnerability's impact was particularly severe given that Flash Player was often installed with elevated privileges on many systems, making successful exploitation potentially devastating for user security and system integrity.