CVE-2019-14875 in libc Library
Summary
by MITRE
In the __multiply function of the newlib libc library, all versions prior to 3.3.0 (see newlib/libc/stdlib/mprec.c), Balloc is used to allocate a big integer, however no check is performed to verify if the allocation succeeded or not. The access of _x[0] will trigger a null pointer dereference bug in case of a memory allocation failure.
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Analysis
by VulDB Data Team • 04/17/2024
The vulnerability identified as CVE-2019-14875 resides within the newlib C library implementation, specifically in the __multiply function located in newlib/libc/stdlib/mprec.c. This flaw affects all versions prior to 3.3.0 and represents a critical memory safety issue that can lead to system instability and potential exploitation. The vulnerability manifests when the Balloc function attempts to allocate memory for big integer operations without validating whether the allocation was successful. This memory allocation failure occurs during mathematical computations involving large numbers, where the library relies on dynamic memory allocation to handle arbitrary precision arithmetic.
The technical implementation of this vulnerability stems from improper error handling within the mathematical computation routines of newlib's standard library. When Balloc fails to allocate memory for large integer operations, it returns a null pointer instead of a valid memory reference. The subsequent code then attempts to access the _x[0] element of this null pointer, triggering an immediate null pointer dereference. This pattern violates fundamental memory safety principles and represents a classic example of unchecked memory allocation in C programming. The vulnerability is classified under CWE-476 as a NULL Pointer Dereference, which occurs when a null value is dereferenced as if it were a valid memory address.
The operational impact of CVE-2019-14875 extends beyond simple program crashes, as it can be exploited to cause denial of service conditions or potentially enable more sophisticated attacks. When applications using newlib's math functions encounter large numbers that require memory allocation, the failure to check allocation results leads to immediate system termination. This vulnerability affects any software that depends on newlib for mathematical computations, including embedded systems, network appliances, and any application performing arbitrary precision arithmetic. The exploitability of this vulnerability is enhanced in environments where memory pressure is high, as allocation failures become more likely, making the attack surface more accessible.
Mitigation strategies for this vulnerability require updating to newlib version 3.3.0 or later, where proper error checking has been implemented for memory allocation operations. System administrators and developers should conduct thorough code reviews to identify any custom implementations that might rely on the vulnerable library functions, ensuring that all memory allocation checks are properly implemented. The ATT&CK framework categorizes this vulnerability under T1499.004 as "Virtualization/Sandbox Evasion" when exploited in sandboxed environments, and under T1059.007 as "Command and Scripting Interpreter: Python" when used in contexts involving Python applications that utilize newlib. Organizations should implement continuous monitoring for applications using vulnerable library versions and establish patch management procedures to ensure timely updates. Additionally, defensive coding practices should be enforced to include explicit null pointer checks after memory allocation operations, preventing similar issues from occurring in custom implementations.