CVE-2016-2177 in OpenSSL
Summary
by MITRE
OpenSSL through 1.0.2h incorrectly uses pointer arithmetic for heap-buffer boundary checks, which might allow remote attackers to cause a denial of service (integer overflow and application crash) or possibly have unspecified other impact by leveraging unexpected malloc behavior, related to s3_srvr.c, ssl_sess.c, and t1_lib.c.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-2177 represents a critical heap buffer overflow issue within OpenSSL versions up to 1.0.2h that stems from improper pointer arithmetic during heap memory boundary validation. This flaw exists in the core cryptographic library that secures internet communications, making it particularly dangerous as it affects the fundamental security infrastructure used by countless applications and services worldwide. The vulnerability specifically manifests in three key source files: s3_srvr.c which handles sslv3 server operations, ssl_sess.c managing session handling, and t1_lib.c dealing with tls1 protocol operations, indicating a widespread impact across different ssl/tls implementation layers.
The technical root cause of this vulnerability lies in the OpenSSL implementation's use of pointer arithmetic for heap buffer boundary checks, where the software incorrectly calculates memory boundaries during allocation and validation processes. When the system encounters unexpected malloc behavior during memory allocation, the flawed pointer arithmetic calculations can result in integer overflow conditions that corrupt heap memory structures. This occurs because the boundary checking logic fails to properly account for potential overflow scenarios when computing buffer limits, leading to situations where memory access operations may exceed allocated boundaries. The vulnerability demonstrates characteristics consistent with CWE-191, which describes integer underflow and overflow conditions, and specifically relates to improper boundary checking mechanisms that allow memory corruption through arithmetic operations.
The operational impact of CVE-2016-2177 extends beyond simple denial of service to potentially enable more severe security consequences that align with ATT&CK technique T1499.3, which covers network denial of service attacks. Remote attackers can exploit this vulnerability to cause application crashes and system instability, effectively creating a persistent denial of service condition that can disrupt critical services. However, the potential for more serious consequences exists, as the heap corruption could theoretically be leveraged for arbitrary code execution under specific conditions, though this would require additional exploitation vectors. The vulnerability's impact is particularly severe because it affects the core ssl/tls implementation that secures web traffic, email communications, and numerous other internet services, making it a prime target for attackers seeking to compromise widespread network infrastructure.
Mitigation strategies for CVE-2016-2177 primarily focus on immediate software updates and patches provided by OpenSSL maintainers, with version 1.0.2i and later releases containing the necessary fixes. Organizations should prioritize patching all systems running affected OpenSSL versions, particularly those handling sensitive communications or serving critical network functions. Additional defensive measures include implementing network monitoring to detect unusual traffic patterns that might indicate exploitation attempts, configuring intrusion detection systems to flag potential heap corruption behaviors, and maintaining comprehensive backup and recovery procedures to quickly restore services if attacks occur. Security teams should also consider implementing application-level memory protection mechanisms and regularly auditing their cryptographic implementations to identify similar boundary checking vulnerabilities. The fix addresses the underlying pointer arithmetic issues by ensuring proper integer overflow protection during heap boundary calculations, thereby preventing the memory corruption that enables both denial of service and potential exploitation scenarios.