Is it undefined behaviour to cast a vector of a class containing 1 POD member to a pointer of the POD type?

Question

I am using OpenAL for playing audio in an SDL2 game, and making some classes to make playing sounds easier. I have a class 'SndBuffer':

class SndBuffer
{
public:

    /* implementation functions */ 

private:
    // the only member of this class (this class does not have any virtual functions either). ALuint is a typedef for unsigned int.
    ALuint m_bufferId;
};

And another class 'SndSource' which contains an std::vector of SndBuffer's.

class SndSource
{
public:
    
    /* other implementation functions */

    ALuint* getBufferIds();

private:
    ALuint m_sourceId;
    bool m_sourceLoaded = false;

    std::vector<SndBuffer> m_buffers;
};

The definition of SndSource::getBufferIds is

ALuint* SndSource::getBufferIds()
{
    return reinterpret_cast<ALuint*>(m_buffers.data());
}

So far, the audio playback works as normal and no errors through OpenAL's alGetError(), however, is it considered undefined behaviour to cast the vector's data to ALuint*?