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Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding a specifically formed message can cause invalid `free()` or `realloc()` calls if the message type contains an `oneof` field, and the `oneof` directly contains both a pointer field and a non-pointer field. If the message data first contains the non-pointer field and then the pointer field, the data of the non-pointer field is incorrectly treated as if it was a pointer value. Such message data rarely occurs in normal messages, but it is a concern when untrusted data is parsed. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.
CVSS 3.1 Base Score 7.1. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L).
CVSS 2.0 Base Score 5.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:S/C:N/I:P/A:P).
This code attempts to tokenize a string and place it into an array using the strsep function, which inserts a \0 byte in place of whitespace or a tab character. After finishing the loop, each string in the AP array points to a location within the input string.
free(ap[4]);
break;Since strsep is not allocating any new memory, freeing an element in the middle of the array is equivalent to free a pointer in the middle of inputstring.
This example allocates a BarObj object using the new operator in C++, however, the programmer then deallocates the object using free(), which may lead to unexpected behavior.
}
free(ptr);/* do some work with ptr here */Instead, the programmer should have either created the object with one of the malloc family functions, or else deleted the object with the delete operator.
}
delete ptr;/* do some work with ptr here */In this example, the programmer dynamically allocates a buffer to hold a string and then searches for a specific character. After completing the search, the programmer attempts to release the allocated memory and return SUCCESS or FAILURE to the caller. Note: for simplification, this example uses a hard-coded "Search Me!" string and a constant string length of 20.
}
return FAILURE;
str = str + 1;
return SUCCESS;/* matched char, free string and return success *//* didn't match yet, increment pointer and try next char *//* we did not match the char in the string, free mem and return failure */However, if the character is not at the beginning of the string, or if it is not in the string at all, then the pointer will not be at the start of the buffer when the programmer frees it.
Instead of freeing the pointer in the middle of the buffer, the programmer can use an indexing pointer to step through the memory or abstract the memory calculations by using array indexing.
}
return FAILURE;
i = i + 1;
return SUCCESS;/* matched char, free string and return success *//* didn't match yet, increment pointer and try next char *//* we did not match the char in the string, free mem and return failure */Consider the following code in the context of a parsing application to extract commands out of user data. The intent is to parse each command and add it to a queue of commands to be executed, discarding each malformed entry.
}//hardcode input length for simplicity/* The following loop will parse and process each token in the input string */
tok = strtok( NULL, sep));
free( tok );/* ignore and discard bad data */add_to_command_queue( tok );While the above code attempts to free memory associated with bad commands, since the memory was all allocated in one chunk, it must all be freed together.
One way to fix this problem would be to copy the commands into a new memory location before placing them in the queue. Then, after all commands have been processed, the memory can safely be freed.
free( input )//hardcode input length for simplicity/* The following loop will parse and process each token in the input string */
tok = strtok( NULL, sep));
add_to_command_queue( command );/* copy and enqueue good data */ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.
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