BF Specification of CVE-2015-0235 GHOST in GNU glibc v2.2, and other v2.x before v2.18

Missing factor (the size of '*h_alias_ptr') while calculating the 'size_needed' size of a buffer leads to reallocation of not enough memory, allowing a pointer reposition over its bounds, which, when used in 'strcpy()' leads to a heap buffer overflow. If exploited, this can lead to arbitrary code execution (ACE) -- everything could be lost.

vendor:product: gnu:glibc:*

Bug Report

Code with Bug

Code with Fix

NVD Entry

TCMType Computation (TCM) class – An arithmetic expression (over numbers, strings, or pointers) is calculated improperly, or a boolean condition is evaluated improperly.
MMNMemory Management (MMN) class – An object is allocated, deallocated, or resized improperly.
MADMemory Addressing (MAD) class – The pointer to an object is initialized, repositioned, or reassigned to an improper memory address.
MUSMemory Use (MUS) class – An object is initialized, read, written, or cleared improperly.
CalculateCalculate operation – Find the result of a numeric, pointer, or string operation.
Reallocate-ReduceReallocate-Reduce operation – Reserve a new smaller space in memory for an object at a new address, reassign the pointer, and release the previous piece of memory.
RepositionReposition operation – Change the pointer to another position inside its object.
WriteWrite operation – Change the data value of an object to another meaningful value.
Code BugCode Bug type – Defect in the implementation of the operation – proper operands over an improper operation. A first cause for the chain of weaknesses underlying a software security vulnerability. Must be fixed to resolve the vulnerability.
   Erroneous CodeErroneous Code bug - There is a coding error in the implementation of the operation.
Data Error/FaultData Fault/Error type – The object data has harmed semantics or inconsistent or wrong value.
   Wrong ResultWrong Result fault/error – Incorrect value – from type conversion or computation.
   Wrong SizeWrong Size fault/error – The value used as size does not match the actual size of the object (e.g., to restrict pointer reposition or index increment/decrement in a repetition statement).
Size Error/FaultSize Fault/Error type – The object size in use is wrong.
   Not Enough MemoryNot Enough Memory fault/error – The allocated memory is too little for the data it should store.
Address Error/FaultAddress Fault/Error type – The object address in use is wrong.
   Over Bounds PointerOver Bounds Pointer fault/error – Holds an address above the upper boundary of its object.
Memory Corruption/Disclosure Final ErrorMemory Corruption/Disclosure exploitable error type – An exploitable or undefined system behavior caused by memory addressing, allocation, use, and deallocation bugs.
   Buffer OverflowBuffer Overflow exploitable error – Write data above the upper bound of an object (i.e., buffer overwrite).
Operation AttributeDefinition
MechanismMechanism operation attribute type – Shows how the operation code is performed.
   OperatorOperator operation attribute – The operation is via a function with a symbolic name that implements a mathematical, relational or logical operation.
   ExplicitExplicit operation attribute – The operation is via a function/method call.
   SequentialSequential operation attribute – The operation is via iterating over the object elements.
Source CodeSource Code operation attribute type – Shows where the operation code is in software or firmware.
   Standard LibraryStandard Library operation attribute – The operation code is in the standard library for a particular programming language.
Execution SpaceExecution Space operation attribute type – Shows where the operation code is running or with what privilege level.
   LocalLocal operation attribute – The bugged code runs in an environment with access control policy with limited (local user) permission.
   UserlandUserland operation attribute – The bugged code runs in an environment with privilege levels, but in unprivileged mode (e.g., ring 3 in x86 architecture).
Operand AttributeDefinition
Name StateName State operand attribute type – Shows the stage of the entity name.
   BoundBound operand attribute – The name is linked to a declared (or inferred) data type, a defined object's data, or a called function implementation.
Data KindData Kind operand attribute type – Shows the category or type of data.
   NumericNumeric operand attribute – A number – a sequence of digits.
Type KindType Kind operand attribute type – Shows what the data type composition is.
   PrimitivePrimitive operand attribute – A scalar data type that mimics the hardware units - e.g., int (long, short, signed), float, double, string, Boolean. A primitive data type is only language defined and is not built from other data types.
Address StateAddress State operand attribute type - Shows where the address is in the memory layout.
   HeapHeap operand attribute – The object is a dynamically allocated data structure (e.g., via malloc() and new).
Size KindSize Kind operand attribute type – Shows the object's limit for traversal.
   UsedUsed operand attribute – A supplied size for an object.