CVE-2015-1781 in C Library
Summary
by MITRE
Buffer overflow in the gethostbyname_r and other unspecified NSS functions in the GNU C Library (aka glibc or libc6) before 2.22 allows context-dependent attackers to cause a denial of service (crash) or execute arbitrary code via a crafted DNS response, which triggers a call with a misaligned buffer.
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Analysis
by VulDB Data Team • 05/09/2022
The vulnerability identified as CVE-2015-1781 represents a critical buffer overflow flaw within the GNU C Library implementation of Name Service Switch (NSS) functions, specifically affecting gethostbyname_r and related functions. This weakness exists in glibc versions prior to 2.22 and stems from improper handling of DNS response data during hostname resolution operations. The flaw manifests when the library processes malformed DNS responses that trigger calls with misaligned buffer parameters, creating conditions where attackers can manipulate memory layout to achieve arbitrary code execution or system crashes. The vulnerability operates at the intersection of network protocol handling and memory management, making it particularly dangerous as it can be exploited through standard network communication channels.
The technical mechanism behind this buffer overflow involves the improper alignment of memory buffers when processing DNS responses through NSS functions. When gethostbyname_r or similar functions receive crafted DNS data, the library's internal buffer management fails to account for memory alignment requirements, leading to memory corruption that can be leveraged for code execution. This type of vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The misaligned buffer condition creates a predictable memory corruption pattern that attackers can exploit to overwrite critical memory locations including return addresses or function pointers, enabling arbitrary code execution within the context of the affected application.
The operational impact of CVE-2015-1781 extends beyond simple denial of service scenarios to encompass full system compromise potential. Systems running vulnerable glibc versions are susceptible to remote code execution when applications make DNS resolution calls, particularly affecting services that rely on standard hostname resolution mechanisms such as web servers, database systems, and network daemons. The vulnerability's context-dependent nature means that exploitation requires specific conditions involving crafted DNS responses, but these conditions can be achieved through DNS cache poisoning attacks or by compromising DNS servers within the network infrastructure. This makes the vulnerability particularly dangerous in environments where DNS security is not properly enforced, as attackers can manipulate DNS responses to trigger the overflow condition in various network services.
Mitigation strategies for CVE-2015-1781 focus primarily on upgrading to glibc version 2.22 or later, which includes patches addressing the buffer alignment issues in NSS functions. System administrators should prioritize patching affected systems, particularly those running network services that perform frequent hostname resolution operations. Additional protective measures include implementing DNS security mechanisms such as DNSSEC to prevent DNS cache poisoning attacks, configuring network firewalls to restrict DNS traffic to trusted sources, and monitoring for unusual DNS response patterns that might indicate exploitation attempts. Organizations should also consider implementing intrusion detection systems capable of identifying potential DNS-based attack patterns and establishing robust patch management processes to ensure timely deployment of security updates. The vulnerability's classification under the ATT&CK framework places it within the System Network Configuration Management and Execution categories, emphasizing the need for comprehensive network security controls to prevent exploitation.