int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
{
    int n, ret;
    unsigned int i, b, bl;

    if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {
        ret = ctx->cipher->do_cipher(ctx, out, NULL, 0);
        if (ret < 0)
            return 0;
        else
            *outl = ret;
        return 1;
    }

    b = ctx->cipher->block_size;
    OPENSSL_assert(b <= sizeof ctx->buf);
    if (b == 1) {
        *outl = 0;
        return 1;
    }
    bl = ctx->buf_len;
    if (ctx->flags & EVP_CIPH_NO_PADDING) {
        if (bl) {
            EVPerr(EVP_F_EVP_ENCRYPTFINAL_EX,
                   EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH);
            return 0;
        }
        *outl = 0;
        return 1;
    }

    n = b - bl;
    for (i = bl; i < b; i++)
        ctx->buf[i] = n;
    ret = ctx->cipher->do_cipher(ctx, out, ctx->buf, b);

    if (ret)
        *outl = b;

    return ret;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.