CVE-2016-4021 in pgpdump
Summary
by MITRE
The read_binary function in buffer.c in pgpdump before 0.30 allows context-dependent attackers to cause a denial of service (infinite loop and CPU consumption) via crafted input, as demonstrated by the \xa3\x03 string.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-4021 affects the pgpdump utility version 0.30 and earlier, specifically targeting the read_binary function within the buffer.c component. This flaw represents a classic case of improper input validation that leads to resource exhaustion through infinite loop execution. The vulnerability manifests when the utility processes malformed binary data, particularly demonstrated through the specific string sequence "�" which triggers the problematic code path. The issue stems from inadequate boundary checking and state management within the binary parsing logic, creating a condition where the function enters an infinite loop when encountering certain crafted input patterns.
The technical implementation of this vulnerability resides in the buffer.c file where the read_binary function fails to properly validate input data before processing it in a loop structure. When the function encounters the malicious input pattern, it does not properly terminate its parsing loop, causing continuous CPU utilization and effectively creating a denial of service condition. This behavior aligns with CWE-835, which describes the weakness of infinite loops or recursion that can lead to resource exhaustion. The vulnerability operates at the application level and requires context-dependent conditions to be exploited, meaning attackers must have the ability to provide crafted input to the pgpdump utility, typically through file processing or command line arguments.
From an operational impact perspective, this vulnerability can be exploited to consume excessive system resources, potentially leading to system instability or complete service unavailability. The infinite loop consumes CPU cycles continuously without producing meaningful output, making it particularly dangerous in environments where pgpdump is used in automated processing pipelines or where system resources are constrained. The attack vector is relatively straightforward since it only requires providing the malicious input to the utility, making it accessible to attackers with basic knowledge of the tool's usage patterns. This vulnerability affects systems that rely on pgpdump for PGP key analysis and can be exploited in scenarios involving file processing, security audits, or automated threat intelligence systems.
The mitigation strategy for CVE-2016-4021 involves upgrading to pgpdump version 0.30 or later, which contains the necessary fixes to properly handle malformed input and prevent infinite loop execution. System administrators should also implement input validation measures when processing PGP files through pgpdump, including file size limits and content sanitization. From a defensive standpoint, this vulnerability demonstrates the importance of implementing robust input validation and boundary checking in parsing utilities, aligning with ATT&CK technique T1499.004 which covers resource exhaustion attacks. Organizations should also consider implementing monitoring for unusual CPU consumption patterns when processing PGP files, as this could serve as an early indicator of exploitation attempts. The fix implemented in the patched version likely includes enhanced state management and proper termination conditions within the read_binary function to prevent the infinite loop scenario that was previously possible with crafted input sequences.