CVE-2016-10739 in C Library
Summary
by MITRE
In the GNU C Library (aka glibc or libc6) through 2.28, the getaddrinfo function would successfully parse a string that contained an IPv4 address followed by whitespace and arbitrary characters, which could lead applications to incorrectly assume that it had parsed a valid string, without the possibility of embedded HTTP headers or other potentially dangerous substrings.
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Analysis
by VulDB Data Team • 08/23/2025
The vulnerability identified as CVE-2016-10739 represents a critical parsing flaw within the GNU C Library's getaddrinfo function implementation. This issue affects glibc versions through 2.28 and demonstrates a classic input validation weakness that can have severe security implications for network applications relying on address resolution. The vulnerability specifically manifests when the getaddrinfo function processes strings containing IPv4 addresses followed by whitespace and subsequent arbitrary characters, creating a parsing behavior that accepts malformed input as valid.
The technical flaw stems from improper validation of input strings during the address resolution process, where the function fails to enforce strict parsing rules for IPv4 address formats. When a string like "192.168.1.1 some arbitrary text" is processed, the function successfully parses the IPv4 address portion while ignoring the trailing content, leading to applications making incorrect assumptions about input validity. This behavior creates a dangerous condition where applications may inadvertently process potentially malicious input without proper validation, particularly in contexts where address resolution is followed by further processing of the parsed data.
The operational impact of this vulnerability extends beyond simple parsing errors to potentially enable various attack vectors including HTTP header injection, data corruption, and application logic manipulation. Network applications that rely on getaddrinfo for address validation may be susceptible to attacks where malicious actors craft input strings that appear valid to the parser but contain embedded malicious content. This vulnerability particularly affects web servers, proxy applications, and any system that processes user-provided network addresses without additional validation layers, creating opportunities for attackers to exploit the relaxed parsing behavior.
Security practitioners should recognize this vulnerability as a manifestation of CWE-20, Improper Input Validation, and potentially related to CWE-129, Improper Validation of Array Index. The issue aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS and T1210 for Exploitation of Remote Services, as it enables attackers to manipulate network service behavior through malformed input. The vulnerability demonstrates how seemingly benign parsing functions can create security risks when they fail to maintain strict validation boundaries, particularly in systems handling network communications where address resolution is a fundamental operation.
Mitigation strategies should include immediate deployment of patched glibc versions, implementation of additional input validation layers in applications, and comprehensive code reviews to identify similar parsing vulnerabilities. Organizations should also consider implementing network monitoring to detect anomalous address resolution patterns and establish strict input validation protocols for all network address processing functions. The vulnerability underscores the importance of maintaining strict parsing boundaries and validating all input according to established network protocol specifications rather than accepting relaxed interpretations that may introduce security risks.