CVE-2023-0216 in OpenSSL
Summary
by MITRE • 02/08/2023
An invalid pointer dereference on read can be triggered when an application tries to load malformed PKCS7 data with the d2i_PKCS7(), d2i_PKCS7_bio() or d2i_PKCS7_fp() functions.
The result of the dereference is an application crash which could lead to a denial of service attack. The TLS implementation in OpenSSL does not call this function however third party applications might call these functions on untrusted data.
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Analysis
by VulDB Data Team • 11/05/2025
This vulnerability represents a critical invalid pointer dereference flaw in OpenSSL's PKCS7 parsing functionality that can be exploited to cause application crashes and potential denial of service conditions. The issue manifests when applications attempt to process malformed PKCS7 data structures using the d2i_PKCS7(), d2i_PKCS7_bio(), or d2i_PKCS7_fp() functions, which are part of the OpenSSL library's ASN.1 decoding utilities. These functions are designed to deserialize PKCS7 data structures from various input sources including memory buffers, BIO streams, and file pointers, making them commonly used throughout the cryptographic ecosystem for processing signed and encrypted data.
The technical flaw stems from insufficient input validation within the PKCS7 parsing routines where the code fails to properly verify the structure and content of incoming data before attempting to dereference pointers within the parsed data structure. When malformed PKCS7 data is processed, the parsing logic encounters unexpected or corrupted data patterns that cause it to attempt accessing memory locations that either do not exist or are not properly initialized, resulting in a segmentation fault or access violation that terminates the application process. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereferences and similar invalid memory access patterns that can be exploited by attackers to cause system instability.
The operational impact of this vulnerability extends beyond simple application crashes as it can be leveraged in targeted denial of service attacks against systems that rely on OpenSSL for processing untrusted PKCS7 data. While OpenSSL's own TLS implementation does not invoke these specific functions, numerous third-party applications and middleware systems do utilize these parsing routines when handling certificate chains, signed data, or encrypted messages from potentially malicious sources. Attackers can craft specially crafted PKCS7 structures that, when processed by vulnerable applications, will trigger the invalid pointer dereference and cause the application to crash, potentially leading to service disruption for legitimate users. This vulnerability particularly affects web applications, email servers, certificate authorities, and any system that processes PKCS7 formatted data from external sources.
Mitigation strategies should focus on immediate patching of affected OpenSSL versions and implementing proper input validation at application layers where PKCS7 data is processed. Organizations should prioritize updating their OpenSSL installations to versions that contain the fix for CVE-2023-0216, typically those released after the vulnerability disclosure date. Additionally, applications should implement defensive programming practices such as validating input data length and structure before passing it to OpenSSL parsing functions, implementing proper error handling to catch and recover from parsing failures, and employing sandboxing techniques to isolate vulnerable components. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through application layer exploitation, and represents a classic example of how cryptographic library vulnerabilities can be leveraged for system disruption. Organizations should also consider implementing network monitoring to detect unusual patterns of application crashes that might indicate exploitation attempts, and maintain comprehensive incident response procedures to address potential denial of service scenarios.